Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science

Submitted by AutoModerator t3_1035nwm in askscience

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Physics, Astronomy, Earth and Planetary Science

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here. Ask away!

26

Comments

You must log in or register to comment.

lunakat6 t1_j2x6u10 wrote

What would happen if we were laid to rest in space? With and/or without an airtight coffin. Would you go on forever, unless you hit something or are pulled somewhere? Would the body decompose or be torn apart? What would be the biggest obstacles for leaving our solar system?

2

pepinyourstep29 t1_j2x8i99 wrote

The body would be subject to the same laws of physics as anything else. Assuming an airtight seal, it would experience minor degradation as it would allow microorganisms present to decompose it for a time before death. A non-airtight seal allows particles to escape, and assuming all microorganisms present die, the body would remain in a preserved state. There would be nothing left to continue the process of decomposition.

Biggest obstacle for leaving the solar system is time. We have the technology to travel across space. We just won't get anywhere in the same lifetime. This is why most science fiction solves this problem with warp drives to teleport across vast distances, cryostasis to wait it out, or use generational ships (where the crew's grandchildren are the ones who arrive at the destination). We currently do not have viable versions of those sci-fi solutions. So the biggest obstacle is overcoming the long trip duration.

5

lunakat6 t1_j2x9oul wrote

Yea but I’m dead. Time doesn’t matter to me, at all. What I more mean to ask is like would it be impossible to get past the asteroid belt or Jupiter’s gravity or some obstacle I don’t know about.

2

pepinyourstep29 t1_j2xbncw wrote

No, those are all obstacles we've already overcome with space probes. Biggest obstacle is just time.

Also I didn't realize your question was about sending a dead body out of the solar system lol

We've sent probes outside of the solar system already. Wouldn't be hard to send an inert coffin the same way.

5

lunakat6 t1_j2xcpzb wrote

Cool. Thanks. So just shot me off into the unknown when my time comes.

1

mfb- t1_j2xueou wrote

An expendable Falcon Heavy can do that on a direct route (no course corrections needed) for $150 million or so.

A partially reusable Falcon Heavy or even smaller rockets can do it with fly-by maneuvers, but then you need course corrections on the way to aim more precisely, which means you need some sort of active spacecraft. The launch gets cheaper but the spacecraft will cost something.

2

lunakat6 t1_j2xvo8d wrote

I think I only really need a lift on a shuttle. No need to waste earths resources/money on a probe or anything. Just open the doors and chuck me out. Or shoot me out like a torpedo.

1

headlessplatter t1_j2xhjm7 wrote

Could Modified Newtonian Dynamics (MOND) be tested by measuring the gravitational effects of Jupiter on our moon? As I understand, Newtonian Dynamics suggests the force of gravity decays by the square of distance, but MOND says it decays somewhat more slowly over great distances. Since our moon is rather reflective, it seems to me we could probably bounce a laser off of it, or if necessary even place a mirror on the moon to facilitate this test. Then, I imagine we could measure its distance with very high precision. If this is feasible, then I imagine we might be able to detect the subtle gravitational effects of other planets on our moon as their distance to our moon changes. (I don't really believe this would work, or else astronomers would probably have tried it, but I'd be curious to know which aspect of this proposed experiment renders it completely infeasible.)

2

mfb- t1_j2xqps2 wrote

The Moon is about as reflective as asphalt, but various missions have left retroreflectors at their landing sites which are routinely targeted with lasers. They can measure the distance with a precision of a centimeter or so, depending on the experiment and targeted retroreflector.

Jupiter, Venus, Mars and Saturn and sometimes even larger asteroids need to be considered in these experiments, see e.g. this publication for a discussion. It's an extremely precise test of our understanding of gravity and the Solar System. Unfortunately it doesn't test MOND directly because a small acceleration from one specific object isn't enough (otherwise you could just say Earth is a billion objects providing a small acceleration each), you need a small acceleration overall. The Moon is not in such a place.

3

paramedic-tim t1_j2xtbbh wrote

How big are the Lagrange points? Like, are the solutions to the equations a small point in space, or are they a large area? How big is the space at the Lagrange points that are usable for satellites, etc?

2

mfb- t1_j2z0ili wrote

The mathematical solutions are points, but the practically useful regions are huge. JWST and Gaia orbit the Earth/Sun L2 point at distances of a few hundred thousand kilometers. Compare this to the 1.5 million kilometers between Earth and L2.

4

pepinyourstep29 t1_j2y6f5i wrote

They're specific points in space, but the stable orbits around them are very large areas thousands of miles wide. Spacecraft can park in that orbit and maintain their position in space with very little fuel.

3

Alkaven t1_j2xnbi6 wrote

My understanding of orbits is that if every particle in the universe vanished except the Earth and the Sun, the Earth would continue in its orbit, because it is in free-fall around the Sun.

My understanding of conservation of energy makes me think that this is impossible. I was told in HS physics that the Earth is constantly accelerating--not because it gets faster and faster, but because it's changing directions by going in a circle ellipse instead of a straight line. F=ma, so it takes force to change the direction. That force is provided by gravity... but here I get confused. Can gravity just provide this force forever? Does that not mean that it's generating energy (from nowhere)?

I'm ten years out of high school so I can't just raise my hand and ask the teacher :( I suspect that I knew the answer to my question at some point and have since forgotten it.

My Google searches somehow turn up all sorts of sources debunking flat earth theory, which is not what I'm trying to do here lol.

1

Weed_O_Whirler t1_j2xrwxj wrote

It doesn't take energy to apply a force. Think of a book sitting on a table. Gravity is pulling the book down (aka, a force pulling down) and the table is pushing up on the book (aka, a force pushing up). And it can just sit there forever. Obviously the table doesn't need energy to do that.

No different than the Sun keeping the Earth in orbit. The energy of the Earth/Sun system stays constant (assuming nothing else in the universe). The force the Sun is providing on the Earth isn't changing its kinetic energy (since kinetic energy only depends on the speed of the object, not its velocity), so conservation of energy doesn't get violated here.

4

Alkaven t1_j2xxtr4 wrote

Wow okay, thanks! I was totally confounding force and energy. The book example is really helpful.

1

Steinway-Grand-D t1_j2yftto wrote

As far as I know galaxies are relativly flat. And I'd say our solar system is also quite flat too, when I look at the orbits of the planets. I've read that the reason is rotation? I can picture a new object coming into a flat system which already has a certain rotation and which will adjust over time to that system. But when and how did the rotation start and why does it seem like the vast majority is flat?

1

pepinyourstep29 t1_j38p65n wrote

It's angular momentum. The rotation starts when gravity begins pulling objects together. They have different masses and speeds so eventually they collapse into a sphere like a planet or star. These initial energies combine into a single moving object, which eventually goes from erratic chaotic rotations to one unified rotation over time.

Then anything of lesser mass will be pulled into the plane of rotation. So everything in the solar system eventually aligns to the same flat plane thanks to the sun's mass and rotation.

Same thing happens at larger scales, where galaxies are roughly flat.

Keep in mind that nebulae and elliptical galaxies exist as well. Under different circumstances things don't always turn out so flat.

2

PeanutSalsa t1_j2zaq3k wrote

Any good documentary/video suggestions that deal with space, the universe, planets, etc?

1