don't want to nitpick but the propagation delay is a bit more than 1 ns per foot. Light travels at 11.8 inch per nanosecond, i.e. 1.017 ns per foot.

Or, to paraphrase dear old Stalin, quantity is a quality all of its own.

Most *people* do that. If only it were limited to academics, life would be easy. But no. Taxi drivers, assistants, hairdressers, dentists, you name it.

The answer, my friend, is blowing in the wind.

We have built machinery that can be used to replicate the same machinery (e.g. 3D printers), but not by themselves. This is hugely difficult: even making simple plastics is hard work and requires lots of resources.

Not by itself. Enough said.

Many people on this thread mention the parallel between aviation progress in the first half of the 20th century and what is happening now with SpaceX, Virgin galactic, and so on.

The difference is essential though. In the beginning of the 20th century we simply did not know enough about fluid dynamics to make aerodynamic flight happen easily. This is still a tough field (turbulence, etc) however we have made huge progress. We can model it relatively well, we essentially know now how to simulate it, etc. The basic equations (Navier Stokes) have been known for a long time, and thank to a huge theoretical, computational and practical effort, we now have cheap, save, available, commercial flight for everyone.

In the case of space dynamics, things are actually fairly simple. We have known about minimum orbital speed, escape velocity, and so on since Newton. We've made measurable progress with chemical rocket engines since then 1950s, but the principles were known at the time. We know how much energy we need to expend to reach space. We know how to navigate space, We know how to do it.

We actually know that we *cannot* do it cheaply at present. What we need to reach a new level is a lot of basic research in materials to build space elevators, better ion drives, perhaps nuclear engines in the future. At the moment we cannot send humans effectively beyond low Earth orbit, and again, this is not cheap. It is not so much a question of entrepreneurship, it is a question of long-term, constant investments. As in several decades.

This is hugely misinformed. In the 19th century people built flying gliders and even a few prototype planes in their backyard. They did not need equivalent 19th century billionaire to bail them out, and very few of them died. This is because the physics of flying is easy and safe, once understood.

Now we already know that the physics of space travel is difficult and dangerous. We've been there. People have died. We have no easy solution. No amount of starry-eyed entrepreneurship is going to change that.

Known physics, the actual economy, and dwindling resources are not on our side.

Actually, the price of travelling by boat has basically increased over time. This is due to the fact that boating is mostly for pleasure. Who crosses the Atlantic by boat nowadays ? Not the poor.

In the case of Virgin Galactic, starry-eyed people believe that some day everyone will get to travel in one of these hypersonic planes, but I don't see that happening. The reason is that it is much much cheaper and immensely less dangerous to fly economy with any carrier. Basically the longest flight is something like London-UK to Auckland-NZ. That currently takes about 30h. Of course it would be nice to do it in 2h but this is not essential. The Concorde did not make supersonic flight happen for the masses. It was only for the very rich / super busy and would have stayed that way forever had the Concorde continued to be exploited.

Concurrently, really going to space (i.e. > 100km altitude, reaching orbital velocity) is going to stay hugely expensive using chemical rockets. There is basically no known technique that can make that cheap and safe, until we build a space elevator. Going to the Moon is essentially pointless: nothing of value to do there, and I'm not sure we will manage to send people to Mars within this century. This is hugely hard, barring some unexpected advances in thrust technology.

This needs to be said a lot more often, however you need a mix of small / large companies. Small companies have very little visibility and cannot invest the millions or billions of dollars needed for some projects.

The only sensible remark here.

Most people think that scientist are strange people who have amassed a huge amount of very precise facts about an extremely specific field, some of which might be useful (facts or fields), but most of which are useless to the common people. The prototype is the scientist lady in the TV series "Bones". Scientists are assimilated to dorks who have not only not an ounce of creativity in them but also no social skills.

In reality scientists need to be extremely creative in their work, and need to have the humility to accept that they know or understand only a tiny amount of the world that is around us. It is very easy and quick to tread into the complete unknown. We cannot at present even reconcile the most established theories we have about the way the world works (relativity and quantum mechanics).

No, that is easy. Most paths in science have never even been tried.

What is hard is to find a path that leads to somewhere. Then just as hard it getting the somewhere you discovered to be accepted by the scientific community. Think plaque tectonics, relativity, quantum mechanics, even something as fundamental as cosmology, and so on.

First you need a friend with an Apple computer and OSX 10.6.8 or later installed. Then you can download the 10.8, 10.9 and 10.10 version of OSX for free on the Mac App Store. If you do not own Apple hardware but want to try these OSes anyway in a VM for instance, it can get a little involved but is generally doable.

Contrary to a somewhat popular opinion among car hotheads, the least reliable component on any car is usually the driver. While on the road, drive safe. If you want to have fun with your car besides enjoying the scenery, go racing.