# Tag Info

14

That's basically the Fermi paradox. It seems likely that there are numerous civilizations in the galaxy, and yet we see no trace of them anywhere. The Drake equation is often invoked to calculate the probability of existence of other civilizations, by compounding several other, more simple probabilities: the probability that a star has planets, that the ...

8

I like the trowing a ball against a speeding train analogy. The important factor is that Jupiter is moving, quite fast. About 13 km/s. The other important factor is that Jupiter is very massive, so it has a lot of gravity and it can draw objects towards it, causing their direction to bend. The tricky concept for a 6 year old is that gravity is a zero-...

6

Yes... In the scenario you describe, you (and the air) will remain at rest, while the torus speeds up. One hopes there are no radial partitions, or, if there are, one comes along to pick you up fairly early in the session. Unfortunately, the rotating torus will impart its velocity to the air in contact with all the irregularities in the wall/floor/ceiling....

6

No. According to the Nasa Venus fact sheet the density of the atmosphere at the surface is ~65 kg/m^3. For comparison, water is 1000 kg/m^3. We only just float in water. So if you were there, in a suit that could somehow withstand the heat (464 C), the "air" would feel thick. Maybe a person could strap on some wings and fly ...

4

This is something that has already been done, so we already have a point of reference. Hayabusa landed on the asteroid 25143 Itokawa in 2005. The mission was considered a success and a sample was returned to Earth. According to sources from the time, the total mission cost was around 170 million dollars and other sources put the development cost of the ...

4

I tend to think the best explanations are the simple ones which explain the core concepts of the concept without getting too fancy or detailed. That being said, I'd just explain what happens during a gravity assist. Cassini flew by Jupiter and when it got close enough Jupiter's gravity began to pull Cassini towards it. This is exactly the same as what ...

4

The Canis Major dwarf galaxy is about 8 kpc from the Sun, but is only 8 degrees below the Galactic plane (and further out than the Sun). So it is about 42,000 light years from the Galactic centre and about 1150 light years below the plane. This almost within the disc of the Galaxy itself. The Galactic disc has a density that varies pseudo-exponentially in ...

3

The farthest Orbital Point from Earth is regulated by the fact that at what point the gravitational pull of the Sun overcomes the gravitational pull of the Earth. I found a post for this on Quora This was the most up voted answer by user Paul Olaru on Quora:- Approximately 1.5 million kilometers. It is limited by the point at which the influence of the ...

3

While "was the Moon landing a hoax?" is starting to be a tiresome genre, the points you make is somewhat legitimate. I am not going to address the issue in general, (Best to go here if you want that) as others have done that better before. But here you go for your issues specifically: "Van Allen Radiation Belt" Yes, it exists, and the radiation is about ...

3

It must orbit the sun in the same direction as the Earth and other planets. The main difficulty in sending a transport to the station will be the the velocity change needed to put the transport into the station's orbit. If the orbit is retrograde with respect to the Earth, then the transport needs to make a massive change of velocity to reach the station, ...

2

Here's a Wikipedia page discussing various theoretical methods of propulsion. It has some very interesting ideas. The one that piqued my interest was the Alcubierre drive. For all intents and purposes it is a warp drive - well, as close as science can get to the fictional engine of The Enterprise anyway. It has been nicknamed the warp drive, I believe, by ...

2

This website has a mathematical in depth analysis of the Apollo 11 translunar trajectory. It looks to be a reasonably reliable resource but I've only had a quick skim through so you should check on the sources cited. There should be enough information there to make a computer program to calculate the orbits.

2

Short answer is easy. Long answer, there's lots of maths involved, and I'm out of practice with my maths, but there's a few basic parts that your students should be able to follow. It's a little confusing, not too bad. We can ignore the Earth's motion around the sun for the most part but not the Earth's escape velocity. Start with Newton's cannonball ...

2

You're actually describing the twin paradox. That's a little beyond Special Relativity, since the astronaut accelerates, and deaccelerates. Since Special Relativity treats only inertial frames of reference, accurate treatment would require some extension towards General Relativity. But you may consider two astronauts, one travelling with constant velocity ...

2

Let's try a crude back of the envelope calculation to get orders of magntitude: The tidal force near the event horizon is of the order of $G M/r^3$ which is something like $10^{18} g/m$. So a probe with a mass of 1 gram and diameter of 1cm would experience about $10^{12} N$ of force trying to "spaghettify" it by accelerating ends of it at about $10^{16} g$ ...

2

If the spacecraft is not accelerating, the astronaut leaves the airlock and just floats outside, not moving relative to it. If the rocket is accelerating they "fall" down towards the stern from the perspective of people onboard; the astronaut would instead say the rocket is accelerating "upwards" and they are just floating. In space, away from gravitational ...

1

One word objection : volunteer ! I cannot see who would volunteer who would also be suitable. There is also the question of what happens when/if they get back ? Sending a brain by itself is pointless. We send humans because they are general purpose problem solving machines capable of independent movement and have hands with opposable thumbs. All a "...

1

Short answer: No. A bit longer explanation: You only have what you bring and grow on your way in your own vessel. Recycling is essential, like exercised already today on the ISS. But you might have to carry it a step further to also recycle the non-water bio-mass and use that as fertilizer to grow your crops. That probably even holds true when you can grow ...

1

A pump can lift water about thirty feet. That's the height where the column of water in the pipe weighs the same as an equivalent column of air (and that's why deep wells use submersible pumps: they push the water up from below, instead of pulling from above and relying on atmospheric pressure to provide the lift). While fuel would be less dense than water, ...

1

I don't know about a spaceship, but the XKCD guy wrote an interesting article about what would happen if Earth was hit by a solid asteroid, travelling at various different speeds: what-if question: Diamond The ship would be a lot smaller than an asteroid, so I think the damage would be a lesser version of these descriptions. (The most extreme case ...

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