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138

You are correct, the centre of the Sun is not the Solar System's centre of gravity. A diagram (courtesy Wikimedia Commons), showing how the barycentre of the Solar System has changed over time. The Sun is affected by the gravity of all planets in the Solar System, but you are right, it is most affected by the two most massive ones; Jupiter and Saturn. ...


123

The force of gravity decreases with distance. It follows an inverse-square relationship... essential to know when you're grinding out the math, but not essential to a conceptual understanding. The fact that gravity decreases with distance means that at some distance, it will be negligible; an object sufficiently distant from Earth may be considered to have "...


94

Escape velocity reduces as you get further away from the Earth. If you proceed upwards at a constant speed of 1 mph (which as noted will require continuous thrust to counteract gravity), you will eventually reach a distance where the escape velocity is equal to 1 mph. Then, you will have reached escape velocity and are no longer gravitationally bound to ...


74

Objects in orbit are attracted to each other, it's just their mass is small enough that the force of gravity between them is infinitesimal. Gravitational acceleration is dependent on mass and distance. In a scenario where a 150 kg astronaut is 10 m from a 80,000 kg Space Shuttle, the astronaut would be pulled toward the Shuttle at 5.336e-8 m/second squared. ...


68

You don't need a space probe. Or an aircraft. Or even a car. NIST has measured the predicted general relativity time dilation due to a change in altitude on Earth of one foot!


61

The problem isn't so much that humans cannot sustain high G forces for any extended length of time: The problem is that rockets cannot. If a rocket could sustain 1 g acceleration for a bit over a day, we could go to Mars in a bit over a day. It instead takes several months to get to Mars because the rockets used to get there only fire for a few minutes. The ...


58

To sum up the answers: the escape velocity is the velocity that, at a given distance, is sufficient to escape the gravitational field so that no additional energy (= acceleration) is needed. That is, if you are 26000 AU from Earth, you don't need any more fuel to counteract Earth's gravity, you just float away. However, when at Earth's surface, you will ...


51

The reason the Space Station is called a micro-g environment rather than a zero g environment is because the Space Station is rotating, because it's in low Earth orbit, and because it's big (for a spacecraft). The Space Station nominally rotates at the orbital rate so as to keep the nadir-pointing windows pointing downward. This alone means an accelerometer ...


51

Using the approximation $$\Delta \mathrm{center}=\frac{m_p}{m_\odot}\cdot\frac{\mathrm{dist}_p}{r_\odot}$$ and data from List of gravitationally rounded objects of the Solar System - Wikipedia: Name Distance Mass/[kg] Mass Distance ΔCenter /km /kg /sun mass /sun radius ---------------------------------------------...


51

No. The moon isn't that big but it isn't exactly small either. The moon's mass is 73,500,000,000,000,000,000,000kg, that's 73 sextillion, 500 quintillion kilograms. If we moved the whole of mount Everest from the earth to the moon (162 Trillion kg, which is completely unrealistic for us to do) then that would equate to an increase of 0.0000000022%, which ...


50

The "gravity of Mars" is not a number but rather a complex field. The most recent is remarkably detailed, made up to spherical harmonics degree and order 120, described by 29,512 coefficients: These maps are made using orbiters (three orbiters in this case), not landers. A lander/rover can give just one local gravitational acceleration and direction, which ...


50

In addition to specific probes like the one mentioned by called2voyage, the effect is significant enough that it affects everyday operations. For example, the GPS constellation needs regular clock corrections because the satellite hardware sits much higher up the gravity well than the ground hardware. The Wikipedia page for gravitational time dilation ...


49

The trajectory was not only "unhindered" - it was enhanced! Knowing mass of the planet you can calculate very precisely how the trajectory of a probe flying by will be affected. You modify the trajectory on arrival in such a way, that the departure trajectory will be exactly as desired. And due to some rather unintuitive physics caveats, you can make it so ...


44

Ignoring the major point that human tolerance of G forces is not the limiting factor on space travel, plenty of thought has been made on how to counteract G forces, not least by 60s sci-fi writers. You can find more information than you ever wanted at Projectrho on this topic. The general gist: for lowish accelerations like 2 G, you don't need to do ...


43

It's complicated! Keep in mind the distinction between weight and mass. On the moon, weight is 1/6 what it is on Earth, but mass is the same. When you hold your arm straight out, you have to exert force equivalent to its weight to hold it in place. So on the moon, that force is much reduced. When you move your arm, you have to exert force proportional to ...


38

Yes, time dilation was experimentally confirmed by Gravity Probe A, launched by NASA on June 18, 1976. The clock rates of two masers (one on the probe and one on Earth) were compared, and it was found that the difference matched what was predicted with an accuracy of about 70 parts per million. To address your question of challenges in designing the ...


35

Short answer, No different from Earth in floating. Buoyancy in water or any fluid is based on the weight of water displaced. Floating is based on the weight of the item displacing water. This is ultimately ends up in comparing densities. If the density of the displacing object is greater than the density of the fluid it will weigh more and sink, if it's ...


35

53 m/s is the approximate terminal velocity of a human skydiver. The terminal velocity of a 7-ton metal dart is quite a bit higher. Larger objects tend to be affected less by atmospheric drag than smaller ones, all other things being equal. Terminal velocity also increases with altitude because the air is thinner. Assuming 7000 kg mass, 3.5 m2 cross ...


33

They used the Lunar Landing Training Vehicle, as pictured below. This had a jet engine to provide 5/6 of the lift needed to hover the vehicle, plus rocket engines that simulated the LM's engines. With the jet running, the LLTV felt like it weighed 1/6 of its actual weight, so it came pretty close to simulating moon gravity.


32

You are confusing velocity and acceleration. If you were to jump standing on the surface of the Earth you might experience 8 m/s which is 17 mph velocity upward, but the acceleration of gravity would act to retard your motion, slowing your velocity down. If you have a high enough velocity, the effect of (de) acceleration can not slow you down ...


32

No, there would be no measurable effect. But we can consider two things: force and mass. Let's imagine we planned very poorly, and always landed our ferry craft in the same Earth-moon orientation (so that by landing, the moon was always pushed "away" from its current direction of motion). The gravitational force between the Earth and moon (the force ...


25

Wikipedia gives $0.51 {km \over s}$ or $510 {m \over s}$ escape velocity, so, no, no leaving Ceres by jumping. Following my earlier calculations, an asteroid of the radius of Ceres would have orbital speed at near-surface orbit of about $336 {m\over s}$, which is way beyond jump strength of anyone as well. Gravitational acceleration on the Moon is $1.6249 {...


25

Thrust won't generate gravity, but it will produce acceleration which may be indistinguishable from gravity to an occupant. Yes, it's possible to simulate gravity by having a spaceship constantly thrusting to travel in a circle, but it would be an awful waste of fuel. Rotating a large object, or pair of objects connected by a tether, to simulate gravity is ...


25

They did not ! This is the trajectory of Voyager 1 at Jupiter. credits wikipedia


24

I think if you are powered (rocket/motor ) you can go at any speed and escape the gravity. The escape velocity is only for objects thrown (projected into space), with the initial velocity and they are not powered.


24

You are correct that Voyager did not change from above escape velocity to below escape velocity shortly after launch. The plot is misleading in that it is just not very accurate right there at 1 AU. The plot lines are kind of thick and a smidge off. Now that I look at it more closely, the escape velocity line in that plot is wrong in other places as well. ...


21

tl;dr: No chance, not even close! The escape velocity from the surface of a round (spherically symmetric) body is given by $$v_{esc} = \sqrt{\left(\frac{2 GM}{r_0} \right)}, $$ showing that it is the $\frac{mass}{radius}$ ratio that's key here, not just the surface gravity given by $$a_{g} = -\frac{GM}{r_0^2}. $$ So since $$v_{esc} = \sqrt{a_g r_0}, $...


20

Let's try and do some math with this. Will use Wikipedia for numbers. Gravity at Pluto's surface: 0.61711215789 $m/s^2$ Gravity from Charon- Pluto's near side- 0.0002724276 $m/s^2$ Gravity from Charon- Pluto's far side- 0.00027242753 $m/s^2$ Centripetal Acceleration- Near side- 0.00001749536 $m/s^2$ Centripetal Acceleration- Far side- 0.00006647414 $m/s^2$ ...


18

While not on the lunar surface, it turns out that in-flight footage of donning and removing suits inside the LM during the Apollo 16 mission does exist. One source is https://www.sciencephoto.com/media/239627/view however the origin is presumably a government document available from other places as well. The perspective is surprisingly good for cramped ...


17

It's fundamentally impossible to measure gravity from an object that is in freefall. This is the first principle of general relativity. What accelerometers will give you is accelerations (linear or rotational) induced by thrusters, atmosperic drag, reaction wheels, etc. vibrations from rotating solar panels, crew-induced forces, etc. The only thing you ...


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