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Comment Re: interstellar mission (Score 3, Informative) 347

For the velocities in question (say > 10% of light speed) the sail would need to be accelerated using lasers -- sunlight isn't bright enough for a large enough proportion of the journey to be useful.

For the same reason it would not get enough thrust from Proxima's light to brake to a stop (or slow down much as all) especially as Proxima is a dim red dwarf.

It might be possible to do better with a magsail, but probably better to focus on recording as much data as possible during a fly-through and then transmitting it back to Earth over the succeeding years, much along the lines of New Horizons at Pluto. With a little cunning the sail can probably serve as the main antenna.

Comment Re:Navigation in space - how do they do it? (Score 1) 77

The probe has a very stable radio transmitter on board. The dishes on Earth can get direction, distance and radial velocity easily and directly from that.
The probe has cameras that can track stars accurately to establish its orientation (it's also spinning which keeps it stable). They also use the probes cameras to photgraph Jupiter its moons and selected stars to get additional information.

The position of Jupiter is known very accurately from previous missions, but New Horizons had to use its camera to refine the location of Pluto from a few million miles out to make final course corrections.

Comment Re:Artillery versus Airplanes (Score 1) 206

If you want to launch truly huge amounts of stuff to orbit it's very difficult to beat Orion and nuclear pulse propulsion. Politically the only way you'd see that happen would be to save the planet.

Wang bullet is cheaper -- dig a deep hole into hard rock. put a nuke at the bottom, then some padding, (sand say) then a very tough payload.

Comment Re:Why Better than Parachute? (Score 1) 206

EIther the parachute opens at high speed in which case it needs to be very strong and well anchored, which makes it complicated and heavy, or it doesn't, in which case it doesn't do you much good. SpaceX don't seem to have much problem getting the stage to just above the pad at reasonably low velocity anyway, using air resistance and rockets.

Comment Re:Don't we have better ways to spend our resource (Score 1) 18

That knowledge won't help us mitigate climate change,.....

It actually might. One of the problems studying climate is that we only have one planet. Exomars (and the larger endeavour of which it is part) might discover atmospheric processes at work on Mars which are important but hard to see on Earth because they are masked by something. Or something even more surprising.

Comment Re:Who cares? (Score 1) 394

Most exams can be written in a way where notes don't really help, or at least they help with things that are not important to test. Exams are supposed to verify understanding, not memorization skills. If your exam can be cheated through with mere memorization, the exam is bogus anyway - it doesn't test what it should be testing.

This is more or less true, although memorisation and recall isn't a bad proxy for understanding, since it's a lot easier to memorise and then explain a load of stuff ifit makes sense to you.

Where it gets interesting is devices with comms capability. Now your ability to solve problems in exams depends on how big and well-trained and well-equipped a support team you can muster, which mostly comes down to money.

For now the problems are solvable. Looking ahead, when every teenager has a surgically implanted (or maybe grown in situ, or even genetically engineered in) comms system in their skull, this is going to get harder. Even defining individual skill or performance, let along measuring it becomes tricky. Indeed, in extreme scenarios, even defining "individuals" becomes tricky.

Comment Re:Only if you ignore the data that contradicts th (Score 1) 446

Here is some data that many people don't know about. We *expect* to see natural warming as the planet climbs out of the Little Ice Age. This is corroborated by the fact that surface is warming faster than the lower tropical troposphere - which is *opposite* to the specific hypothesis of AGW.

Could you state that specific hypothesis please?

Comment Re:Stop arguing about the details... (Score 1) 446

I am all in favor of less CO2 emissions and more efficiency. I just think it is a waste of time, at this point, to make that what we throw all our money at, because it isn't going to make a bit of difference in the short term.

Do you have any evidence for this? Thousands of people who have spent their entire careers working on this disagree with you in thousands of pages of peer-reviews papers.

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