I don't know how you've ended up with that!

Velocity = Frequency * Wavelength.

Speed of sound is about 340 m/s in air at one atmosphere.

Hence wavelength = 340/20,000 = about 0.017m, (17mm).

My suspicion is that you've used the speed of light instead of the speed of sound here...

Check out Zooniverse - https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fwww.zooniverse.org%2F - there's a lot of projects that are helped by citizen science. A nice platform where human powered processing can contribute. I don't think there's the kind of review etc you're asking for, but it does have a very nice interface for building your own project, contributing to others etc.

A single shot device like a railgun cannot launch something into orbit. You need a second impulse to alter the trajectory to achieve orbit. The reason is that orbits close - they're ellipses (or circles). So with a single shot device you either launch something to infinity, or you have it crash back into the planet as its orbit intersects the point of origin.

What you'd need in this scenario is either something to collect the sample already in low orbit, or a container with a thruster of some sort to force the trajectory into orbit. Either case increases the difficulty considerably.

No. Von Braun learnt from Ley and Oberth, and did a PhD in physics specializing in rocketry at Friedrich-Wilhelm University.

"Self-taught rocket scientist..."

This is gonna be good.

Is a "farther" a distant dad?

The wake behind a ball is NOT like the tail of a comet - the tail of a comet points (approximately*) away from the sun, not opposite to the direction of motion.

Comet tails are not caused by some kind of drag - the comet moves in a vacuum in (almost**) geodesic motion around the host star.

* Yes, there are actually two tails, dust and gas, directly not exactly away from the sun. The point is really that comet tails do not follow comets around the sun.

** M_comet/M_sun is normally pretty small, etc.

Physics 101 baby ;-)

Drag racing is normally quite a good intro topic for 1D kinematics - you can do constant acceleration, look at the real relations between velocity, acceleration and position etc. It's nice because you can push the students to understand when equations are and are not valid, and what they can actually work out with limited information.

I agree - that's why I said throughout that my estimate was conservative. Assuming constant acceleration gives the slowest possible 0-60, hence the max time from these figures is 3.25 seconds.

Interestingly if you look through the pictures in TFA you see that the speed has just about topped out at the 1/8 mile mark. If you run the numbers there, you get an acceleration around the 10.5 m/s^2 mark, which indeed gives about 2.5s for the 0-60 time.

And yes, clearly the car is not designed with cornering in mind.

I would hope one of the requirements to be a "street-legal" car is that it can turn, at the very least...

If we make a horrendous assumption of constant acceleration we can get a maximum on it's 0-60 time:

s=1/2 at^2, t=9.87s, s=400m gives a=8.21 m/s^2

60mph = 60*1600/3600 m/s= 26.67 m/s

t60 = 26.67/8.21 = 3.25 seconds.

So we can conservatively conclude this vehicle does 0-60 in under 3.25 seconds.

Someone with better knowledge of the acceleration/velocity curves of cars can probably correct me on this, but I'm assuming that acceleration reduces with velocity rather than increases, due to wind resistance etc. If this is right 3.25 should be considered a maximum - if the acceleration reduces above 60mph, say, then the car must accelerate to this velocity in even less time to get a quarter mile in 9.87s.

From the data given we can only conclude that its top speed is somewhat higher than 400m/9.87s = about 40m/s or 90mph, but of course that would assume instant acceleration to 90, in all likelihood its top speed is far higher.

Noise. All kinds of noise.

The system is an interferometer - basically two lasers set up in a large L shape with mirrors (massive simplification). When the lengths of the arms are the same, the beams cancel, when they differ a signal is recorded.

Now, the differences in length due to a gravitational wave is tiny, and the problem that kept LIGO from their detection is that there are huge numbers of sources of vibrations around the same frequencies as expected from gravitational waves that have far larger amplitudes. Thermal vibrations, for example, are a killer for experiments like this.

The waves themselves have almost exactly the waveforms that were predicted - the template fits from simulations match amazingly well in terms of amplitudes, frequencies and their evolution. What stopped experiments like this from making the observation was simply a lack of technical skill to make a precise enough instrument. Following the development of LIGO over the last decade, this is precisely what everyone working on the project said - once the noise curve is reduced to form Advanced LIOG (recent upgrade) the noise would be sufficiently small than an integrated signal against a template would be clearly visible, and now it is.

Think about when the light at the edge of your calculation was emitted, and where that place is now. The definition of the observable universe goes roughly as follows:

Consider a photon emitted from a point at the big bang (really CMB, but we can substitute with a small change) that gets to us today. How far away is an object that was at rest (with respect to the homogeneous cosmological spatial slice) at that position now?

It isn't as simple as multiplying up these numbers, as the Hubble parameter changes over time. What you really want to do is track the world-line of an imaginary stationary object from which the light was emitted, and that of ourselves, integrating the Hubble rate given by Friedmann's equation given our best guesses at the types of matter/radiation dominating evolution. That's where the 28Gpc (about 90 billion light years) figure comes from.

The point that emitted the photon is now no-longer observable to us, and never will be again if the current models are correct - it's exited our past light cone, as does more and more of the spatial slice every instant. So there's no contradiction between the point moving away from us 'faster than light' and it having it in our observable universe. One is a calculation done about two spatially separated points at a fixed time, the other is understanding the content of our past light cone.

Hope that helps!