# Tag Info

## New answers tagged solar-system

4

It's easier to dispel this with biology and geology than with physics. That our circadian rhythms are 25 hour long is based on research done in 1962 that was later found to be faulty. For more recent research, see, for example, Czeisler, et al. (1999), "Stability, precision, and near-24-hour period of the human circadian pacemaker," Science 284.5423 : ...

1

SciShow covered this and their sources are in the video description. It probably can't happen, but it depends on your tolerances. Planetary alignments have a "quality" which is how far apart in the sky the planets are allowed to be and still considered in "alignment". All planets lined up in a nice straight line from the Earth to the Sun? Almost ...

0

according to some theories (like big bang) the planets are parts of greater bulks and as gradually they collide and teared apart (after becoming cold) they have gotten a speed due to the explosion and then they have stuck in the gravitational field of bigger planets and stars and rotating in vacuum around them so they don't lose their velocity due to some ...

0

Let me answer another component: where the initial energy for their movement came from. Imagine two bodies separated by a large distance. In this case, the gravitational pull is small and the gravitational potential is low. Their relative velocities are just about zero. For all intensive purposes, our energy accounting is zeroed out. KE=0 GE=0 (kinetic and ...

2

This article covers the question Radiation is divided into two categories - ionizing radiation and non-ionizing radiation. Ionizing radiation is radiation with sufficient energy to remove electrons from the orbits of atoms resulting in charged particles, and it is this type of radiation that is evaluated for purposes of radiation protection. ...

11

As stated in other answers it is how much the gravitational force is different by on opposite sides of the earth that creates the tides. You can still show this using $a=\frac{GM}{d^2}$ but you need to consider the difference, not the absolute force on the earth. The sun while much more massive is just far enough away that it is getting to a much flatter ...

8

The highly upvoted answer is right but to make things much simpler: Tides are based on the change in gravity, not the gravity. That means they drop off at the cube of the distance rather than the square of the distance like gravity itself does. Thus the object with the most gravity isn't necessarily the one that causes the most tide.

0

People who are studying something something generally use a frame of reference which is reasonably close to the things of interest. While it might in theory be possible to measure the stature of a man by very accurately determining the distance from the center of the Earth to the bottoms of his feet, as well as the distance from the center of the earth to ...

36

Tides are caused by the gradient of the gravitational field - so the tidal "force" experienced drops with the third power of the distance. This means that the relative strength of the tides should go as ratio = \frac{M_{moon} \cdot D_{sun}^3}{M_{sun} \cdot D_{moon}^3}\\ =\frac{7 \cdot 10^{22}\cdot (1.5 \cdot 10^{11})^3}{2\cdot 10^{30}\cdot (3.7\cdot ...

62

What is important for tidal forces is not the absolute gravity, but the differential gravity across the planet, that is, how different the gravity is at a point on the surface near the sun relative to a point on the other side. Because the Sun is far away, gravity doesn't change much between the two extremes on earth. However, if you compare it with the ...

0

As shown in a previous answer, Assuming they have the same density (the Sun's average density is not much smaller than that of the moon) , if they had the same apparent size in the sky, then the mass M of the object will grow as r3 (because M=4/3ρπR3 and R=θr), so the force actually grows linearly with r. this implies that for same apparent size and ...

2

Tidal forces drop rapidly with distance - the derivative of $1/t^2$ is $-2/r^3$. Further, the difference in radius of the orbits of Earth and Mercury is a little more than a factor 3x and radius of mercury is about 2.5x smaller than that of earth. From the orbits we gather the tidal effect is 27x smaller - from the radius we gather that moment of inertia is ...

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