Category Archives: Tech

Escape Velocity

Escape Velocity is commonly described as the minimum speed an object must reach to escape the Earth (or other celestial body) into space. But this definition is ambiguous and can be misleading.

You can escape the Earth at walking speed, if you could walk straight up; you don’t need anywhere near escape velocity. Imagine a rocket launch; in the first few seconds just as it starts to move, it’s going up at walking speed. Theoretically, it could throttle back the engines to maintain that slight upward speed all the way into space, so long as it didn’t run out of fuel or become unstable. A space elevator could also leave Earth at mundane speeds.

The key to this ambiguity is escape velocity applies to a free body, an object that is passively moving according to the laws of physics, having no thrust of its own. In other words, if a rocket achieves escape velocity, it could at that point turn off its engines and it would still escape the Earth. Intuitively it seems the higher the altitude, the slower the escape velocity. This turns out to be correct.

Escape velocity is easy to understand and derive mathematically with some creative thinking. Imagine 2 objects in space (a big one and a much smaller one, like the Earth and a stone) surrounded by vacuum, no other objects. So there is no friction and no other bodies exerting gravitational pull. Suppose the stone is at rest relative to the Earth and almost infinitely far away. The gravitational pull is effectively zero. Imagine the stone precariously balanced just on the outer rim of Earth’s gravity well. Then you nudge the stone just a smidge toward the Earth, so it crosses that rim and the Earth starts pulling on it (and vice versa). It starts out slow, but accelerates toward the Earth incrementally faster and faster.

Eventually, when the stone reaches the Earth it will be moving very fast. Escape velocity is the speed it is going just before it smashes into the Earth. Or if it misses the Earth, it’s the speed at its point of closest approach. More correctly and completely, the stone is always traveling at escape velocity at every moment along its path. The escape velocity for that distance from the Earth, is the speed at which the stone is moving when it’s that far away.

Note: the bold face statement above is the nut of this explanation. When you grok its fullness, you grok the fullness of escape velocity.

That’s because of conservation of energy. When the stone was at the rim of Earth’s gravity well, it had a lot of potential energy. At the point of closest approach, all that potential energy has been converted into kinetic energy. Assuming no atmosphere, no losses, the two energies are equal. So as the stone speeds past the Earth, slowing down due to the same gravitational pull that sucked it in, that kinetic energy is converted back into potential energy. So it must reach the exact same distance away when it peters out and eventually stops.

The direction of motion is irrelevant to escape velocity. Normally this seems counterintuitive, but understanding escape velocity with our theoretical example, you can easily see why direction doesn’t matter. At that point of closest approach, it doesn’t matter what direction the stone is moving relative to the Earth. It could be nearly straight up (can’t be exactly straight up, or it wouldn’t have missed), or nearly horizontal. If it’s going horizontal, it has to travel further to escape, but being horizontal, gravity isn’t pulling it as hard. These conflicting factors are equal and cancel each other. All that matters is the altitude (distance of closest approach), because the speed depends only how much energy it’s gained from Earth’s gravity field.

If, at that point of closest approach, the stone were moving any slower, then it would have less kinetic energy, and it will not go as far away. That means it won’t make it to the rim of Earth’s gravity well, so it will still be inside the well, reverse direction and eventually come back to Earth. So escape velocity is the minimum speed a free body can have, and escape the Earth.

Of course, in the real world direction does matter. The Earth has an atmosphere that creates a lot of friction and energy loss at high speeds. If you go straight up, you’re in the atmosphere for a shorter time, less energy loss. If you go horizontal, you’re in the atmosphere longer and will lose more energy.

Here is the mathematical derivation:


Updating Celestron Telescope Firmware

Here’s how I update the firmware in my Celestron 6SE telescope from my Ubuntu Linux system. There’s another nice guide here, but it didn’t work on my computer until I figured out the trick below of changing the port name.

Kudos to Celestron for writing the software in Java so it can run on any computer, Windows, Mac or Linux!

My scope has a phone-type connector to the handset and came with a cable that is a 9-pin serial on the other end. Plug this cable into your computer’s serial port and into the bottom of the handset. While the scope is off, hold down the handset Celestron & Menu buttons while turning it on. The handset will say Boot Loader Serial or something like that to indicate it’s in firmware update mode.

Now, find the Linux device file for your serial port by entering this command: dmesg | grep tty

My output looks like this; yours may be different:

[    0.000000] console [tty0] enabled
[    0.671956] 00:06: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A

On my computer, the serial port is /dev/ttyS0

Check this device file’s permissions and ensure you can read & write it. Typically you need to be in the dialout group, or just chmod the device file to 666 to open it to anyone.

Follow Celestron’s instructions to download the CFM software from their web site. Once installed, go to its directory and run it with Java: java -jar CFM.jar

When it starts it will tell you it can’t find the serial port. Select Options|Connections from the menu. In the dialog that appears, you’ll notice it says COM4 (or something similar) as the serial port name. Replace this with ttyS0 (or whatever your port’s name is).

Now click Seek Devices from the app main screen and it will find your telescope. Click the main screen Update button and CFM will find and download the latest firmware for your scope and install it.

How to Shrink Virtualbox VDI Volumes In-Place

In my case, Ubuntu 16 is the host OS, Windows 7 is the guest OS, with Virtualbox 5.0.40.

Before starting, ensure your Virtualbox is a VDI file. VMDK files can’t be resized–though they’re useful for other reasons, being compatible with other virtualization software like VMWare.

First, run the guest OS. Defrag the drive. Defragging crams all the files together with contiguous unused space at the end of the drive instead of scattered around. Then run: sdelete c: -z. You must run this from a command prompt having admin privileges. This step writes zeros across the unused space, which is critical because VirtualBox can’t compact the VDI unless the free space is full of zeroes. The sdelete command takes a long time after reporting 100%, appears to be hung. Be patient and let it finish.

Now shut down the guest OS. From the host OS command line, run: vboxmanage modifyhd file.vdi compact. Here, file.vdi is your VDI file.

Your’e done. The VDI file will be smaller. It will grow automatically as you use more of the guest OS disk space.

Note: don’t use the guest Windows 7 OS file management to shrink the volume. The free space it creates can’t be compacted by VirtualBox.

Tip: Battery Saving for Android 6 and 7

Recently I noticed the location icon sporadically appearing on my Galaxy Note 4 phone for no apparent reason. Something was pinging location. This has a double-whammy on battery: using the GPS (or attempting to without a clear sky), and waking up the phone from sleep. The battery usage screen showed Google Play services as a primary consumer.

The fix took a while to find but it was simple: Google Location History. This is an Android service that periodically checks and logs your location. Google uses this to improve various services like search and maps.

I don’t care about this. Search results and maps work just fine, well enough for me, without having my location history. And I don’t use Google Now. And I don’t like the idea of my phone constantly tracking my location.

Here’s how to disable this, which noticeably extended my battery life:

  • Go to Settings / Location.
  • Scroll down to the Location Services section.
  • Tap Google Location History
  • Tap the slider in the upper right hand of the screen to turn it off.


Galaxy Note 4 Rooted Update

When your phone is rooted, the built-in system update won’t work. It will refuse to update itself. If you want system updates you must install them manually. This is how I do this on my Samsung Galaxy Note 4.

First, back up your phone. You should do a full binary backup with TWRP, and also back up individual apps (and their settings) with Titanium Backup. Do both because each serves a different purpose. A TWRP backup is useful if the update goes awry. It’s a full binary image that restores your phone and all its apps to its prior state. But you can’t restore individual apps. A Titanium backup captures your apps and their setups & data, which can be individually restored into a new system. But it includes apps and system data only, so it doesn’t help if the install goes awry.

In short, if your update is successful you’ll restore your apps from Titanium Backup. If your update fails you’ll restore your entire system from the TWRP backup.

Next, get the latest firmware. You can do that SamMobile. It’s typically a 1-2 GB download because it includes everything: boot loader, modem, Android, Google Apps, etc. After downloading the ZIP, unzip it to get an MD5 file that’s about twice as big.

Next, boot your phone to download mode: turn it off, then press and hold Power, Home and Volume Down. Connect it to a Windows PC (or VM) running Samsung’s Odin app. Make sure Odin recognizes the device when you plug it in. From Odin click the AP button, pick the MD5 file you downloaded from SamMobile and send it to your device. The phone will show a bar graph as the data is sent. When it’s done, Odin will show whether it was successful and the phone will reboot.

Give the phone a long time to reboot; don’t worry if it takes several minutes. When it comes up, all your apps should still be there because Odin doesn’t wipe the data partition. But your phone will no longer be rooted and the TWRP recovery will also be wiped.

To restore TWRP and root, follow a similar process. First download the TWRP tar file. Boot the phone to download mode and used Odin to push it to the device, as above. But this time, before pushing it, disable auto reboot in Odin (it’s on the Options tab). When the TWRP push is done, power off the phone, then boot it to recovery mode: hold Power, Home and Volume Up. It should boot into TWRP. Now you have restored TWRP recovery.

To root the phone, copy the SuperSU ZIP file to the phone. You can do this via a standard USB file transfer to your phone while it’s booted normally, or you can do this while the phone is  booted to TWRP, using adb file push from your PC command line. Then boot to TWRP and install the ZIP. The SuperSU install script will print stuff on the screen; follow the instructions, which is to reboot the phone when the install is done, and let it reboot itself a couple of times to complete the install.

When you’re done, you’ll have the latest OEM firmware update, with TWRP and root. And it should not wipe your data or apps.

Galaxy Note 4: Spurious Wakes and the Home Button

I love my GN4 phone but it has a problem: it wakes up (screen turns on) randomly while in my pocket. When this happens, the screen is on and contact with the inside of my pocket causes spurious random screen touches which is highly dangerous. Not just the risk of butt-dialing people, but it could also change settings, uninstall apps, etc.

The cause is simple. The home button wakes the phone, and it protrudes slightly, so it’s very easy to trigger while in a case or pocket. The best fix would be a system checkbox enabling users to prevent the home button from waking the phone. When disabled, the only way to wake the phone would be the power button, which is quite firm and never is accidentally pushed.

However, Samsung’s response to this is idiotic: “don’t put it in your pocket”. Because Samsung has their heads in the sand (to be polite) on this, users have come up with their own solutions,

One is to install Xposed. But this is a sledgehammer. It works but I didn’t want to deal with it.

Since my device is rooted, I figured there must be some system config text file I could edit to get what I wanted. I didn’t find exactly what I wanted–simply disable wake on the Home button. But I found something close enough that works: swap the Home and Menu buttons.

On my GN4 running T-Mobile Android 6.0.1, the file to edit was: /system/usr/keylayout/Generic.kl

Change two lines:

key 172 HOME
key 254 APP_SWITCH

So they read:

key 254 HOME
key 172 APP_SWITCH


The App Switch (Menu) button will now be Home button, and vice versa. And the Home button will not wake the phone. Nor will the Menu or any other button. The only way to wake the phone will be to press the power button.

My phone no longer randomly wakes up in my pocket. No more butt-dialing, accidentally rearranged home screens, uninstalled apps, or hot phone. No more wasted battery consumption. It’s a bit strange to get used to swapped Menu & Home buttons, but the benefits are worth it.

Note: I tried editing /system/usr/keylayout/gpio-keys.kl and removing the WAKE_DROPPED indicator. Disabling the home button’s WAKE feature without remapping buttons would be ideal. But this didn’t work; it had no effect. Apparently it worked in prior versions of Android, but Samsung changed the way keys are mapped in 6.0.1.

Ubuntu VLC DAC Audio

I recently got a JDS Labs Element DAC + headphone amp. I drive it from my Ubuntu desktop using VLC as the audio player. It’s plug and play – no drivers needed. However, best results come after applying a few tips:

VLC Audio Device: The DAC has 17 output devices that appear in VLC. Which one to use? Use Pulse Audio if you want to hear a mix of all audio on the computer. Pulse Audio mixes all sources and resamples them if necessary to a common rate. Use JDS Labs Element DAC, USB audio direct hardware device without any conversions if you want to hear the audio track in its native sampling rate & bit depth, and nothing else. I prefer this for best sound quality.

VLC Output Module: use Pulseaudio audio output if you want to hear a mix of all audio on the computer. Use ALSA audio output if you want to bypass Pulseaudio to hear the audio track and nothing else.

VLC occasionally stopped playing and popped up an error saying “Device or resource busy”. If you’re using ALSA, only one app at a time can use the device. For example, if the browser tries to play a video it can steal the device from VLC. Also, VLC seems to have a bug in which it occasionally steals the device from itself when switching tracks. Adding a udev rule made this happen far less often. Add a file called 41-jdslabs-dac.rules to directory /etc/udev/rules.d. Make the contents like this:

# JDS Labs Element DAC
SUBSYSTEM=="usb", ATTR{idVendor}=="262a", MODE="0666", GROUP="plugdev"

This makes the JDS Labs DAC accessible to any Linux user.

Audio Glitches: Occasionally, once every hour or so, the audio will stop for a moment, then resume. I believe this is because the JDS Element uses USB adaptive mode, not async. This makes it compatible with more computers. Some people claim that adaptive move has more jitter and lower sound quality, but measurements belie this claim.

More audio glitches: Occasionally I would hear tics in the music, as if the computer CPU were too busy to deliver audio. Re-nicing the VLC process to -15 fixes this.

Net Neutrality is Misguided

This article in Tech Crunch sums the argument in favor of Net Neutrality:

Everyone agrees on the end: we want an open internet. But there’s more than one means to that end. We disagree on the means, not the end. The Senate Democrat perspective assumes that ISP companies will infringe the speech of their customers or restrict their traffic flow, unless government regulators prevent this. So they conclude we must grant government this new power.

This perspective is misguided in two ways. First, it assumes new government powers are the only way to prevent ISP companies from restricting content or traffic flow in ways that harm consumers. Second, it ignores the risk and cost of these new government powers.

Two alternatives to achieve the common goal of an open internet are regulation and competition.

Net Neutrality regulation means rules controlling how to handle data content and movement. These rules must go through multiple approvals and public comment. They are necessarily reactionary and lag technology and innovation. They are also detailed and complex by nature. This attracts rent seeking and lobbying for loopholes by ISP companies, which makes the rules even more complex and inefficient. This increases the complexity and cost of doing business, which reduces innovation, rewards established companies and deters new providers from entering the market. That means higher prices and less consumer choice.

For one example, consider T-Mobile’s zero-rating video data. Most of their customers loved this service, and the ones who didn’t could opt out at no charge. Yet providing this service got T-Mobile hauled in front of the FCC to explain themselves to regulators. They were exonerated, but this positive outcome was not preordained. It cost them thousands to defend themselves and they could have been subjected to massive fines. When ISPs get hauled in front of the FCC to testify every time they do something regulators didn’t anticipate, say goodbye to innovation.

An example the Senate Democrats use is “fast lanes” vs. “slow lanes”. This is a red herring. Some kinds of traffic, like video, consume far more bandwidth than others. For the internet to function properly, these different kinds of traffic must be handled and routed differently. In short, there already are “fast lanes” and “slow lanes” —  it’s a technical necessity. The question is how we pay for them. Blanket rules like Net Neutrality risk creating a tragedy of the commons, where everyone uses bandwidth but nobody invests in developing it, or forces everyone else to pay the costs of heavy bandwidth users, which encourages over-consumption, reducing quality of service for everyone.

Yet the Senate Democrats do have a certain logic. With only a handful of monolithic ISP companies, there is no real competition and some form of regulation like Net Neutrality becomes necessary. However, as citizens and consumers, we should not accept the inevitability of having only a handful of monolithic ISP companies. And we surely should not pass new regulations like Net Neutrality that will foster and lock in this dystopian future. Net Neturality is self-actuating and self-perpetuating. It creates and exacerbates the very problems it intends to prevent, as it purports to solve them.

In short, it is naive to believe:

  • That Net Neutrality regulations will stay ahead of fast-changing technology and creative interpretation by ISP companies.
  • That a distant federal bureaucracy will make better decisions about how to allocate bandwidth and handle traffic, than ISPs directly negotiating with each other and seeking customers.
  • That Net Neutrality rules will be immune from rent-seeking, carved-out loopholes and other forms of regulatory capture by big ISPs.
  • That these complex rules won’t raise the cost of business, restricting innovation, competition, and consumer choice.

Consider the alternative that the Senate Democrats ignored: competition. With competition, if one provider does something you don’t like, vote with your wallet and switch. You can switch at any time, for any reason: terms, privacy, cost, etc. Your vote hits the ISP where it counts: financially. Complex rules don’t bother them or protect you; their lawyers and lobbyists are better than yours, and are helping draft those rules.

Under competition, the rules we need are simple: prohibit fraud and establish property rights for access. There is no need for complex rules micro-managing data content and movement. This reduces rent-seeking and lobbying and keeps the cost of doing business low. Without complex rules dictating how to run their business, companies are free to innovate in technology and service to differentiate themselves, much like T-Mobile did for telecom.

But this works only under true competition. That means every person has a choice of several providers (not just two) and can switch between them quickly, easily, and cheaply. Unfortunately, we don’t have this in the USA. Why not? Primarily because multiple layers (local, state, federal) of complex regulations lock in existing ISPs and make it expensive for new companies. The reason some ISPs get away with bad behavior, like famously bad customer service and high prices, is because their customers have no alternative. Over-regulation protects them from competition. Adding even more more layers of regulation (e.g. Net Neutrality) will fix this like throwing gasoline on a fire.

Far better to address the root cause. Unwind the layers of complex regulations and municipal property access rules that lock in ISP companies and block competition. ISPs already are too much like utilities. This is the problem, not the solution.

LineageOS is Alive!

Last night I installed LineageOS 14.1 on my Galaxy Note 8 tablet.

I’ve been running CM 13 on this tablet for the past year or so and it works great – stability, performance, battery life. But the last build was Christmas Eve 2016, then Cyanogenmod died. I’ve been watching CM relaunch as LineageOS. They now have a home site and are running weekly builds for many devices. The Galaxy Note 8 happens to be one of these devices – with more to come.

The installation procedure is the same as CM. First, install TWRP recovery. You should do this no matter what build you’re running, even stock, because it has great features like full backup & restore. There are plenty of install guides. I had it installed already. Then, install LineageOS:

  • LineageOS Zip
  • Open Gapps Zip – use version 7.1 for LineageOS 14.1.
  • SuperSU Zip (if you want root)

The root ZIP provided by LineageOS did not work – TWRP had an error trying to install it. I used SuperSU instead, and it worked perfectly.

I’m still restoring backups & such, but first impression is that LineageOS 14.1 seems solid and fast. I’ll report back later after I get some time to use it.

Thoughts on the Dark Forest

I recently read Cixin Liu’s Three Body Problem and Dark Forest. This blog entry is a spoiler, so you may want to stop reading this if you plan to read these books.

Fermi’s Paradox is a key concept and plot element, particularly one explanation for it called the Dark Forest, tied to character Luo Ji’s axioms of life in the universe:

  1. Life’s goal is to survive
  2. Resources (matter & energy) in the universe are finite
  3. We can never be sure of alien life’s true intentions
  4. Distances between stars impair communication

Conclusion: (3) and (4) create a chain of suspicion making conflict inevitable.

I am not convinced. This is fixed-mindset, zero-sum thinking, similar to the flawed economic thinking behind Malthusian doomsday predictions and protectionist trade policies here on Earth. The above rules are not unique to outer space. The same could be said of different cultures here on Earth – every man presents a threat to all others as they must compete to secure the limited means of survival, leading to inevitable conflict. During some historical periods – primarily in pre-agricultural tribal societies – this was true. Yet today it is false. We have Human societies of size, complexity and interdependency that would be unimaginable to prior generations. Why?

Two key factors. First, the increased productivity of division of labor. Second (and a part of the first), Ricardo’s theory of Comparative Advantage. It was not love or enlightenment that caused Humans to stop fighting each other over the limited resources Nature provided (as animals do), and instead cooperate to create new resources making everyone better off. It was recognition of these fundamental economic facts.

The same applies to space exploration, even more so. Cixin Liu misses this point entirely and falls for the simplistic zero-sum thinking that has duped many before him. Items 1-4 are true, yet the conclusion does not necessarily follow. He’s missing an important 5th axiom: The potential benefits of cooperating with alien life are so tremendous they cannot be measured. When balanced against risks (3) and (4), conflict is no longer inevitable. The result may end in conflict or cooperation, depending on the situation.