There is lot of garbage out there, right above your head

Hi,
no no, I do not speak about the stuff in your house, though who knows how it looks like. I mean a junk on the orbit of Earth.

Earth from space, surrounded by small white dots

Stuff above your head in low Earth orbit and geosynchronous orbit.


This stuff which is hundreds of kilometers above may not really concern you, if it falls down it should burn up in the atmosphere.

Actually it should concern you since your life almost completely depends on satellites above that are still working.

Those that are still working are at the same time endangered because of those that are not working. How bad is it?

Well on one side not so bad. No huge catastrophy happened, yet.

On the other side this is just a matter of time, the thing that should concern us most is ISS of course since there are some people there. When some things fly on those heights, they tend to do it very fast, even 17,500 miles per hours. Take for example a cat, not that there are any cats 400 kilometers above Earth, she usually weights about 4,5 kilograms. What is the momentum of the cat?

The momentum is about 126,708.75 kg*km/h. This is a lot, how much?

Yes, this is your cat which is just going to destroy something

The same momentum has a car (1,590 kilograms is regular midsize) driving at the speed of 80 kilometers per hour.

Now just imagine a car crashing into something at 80 km/h, it will do a great deal of damage and same damage can create a cat flying on orbit (or 353 cats at the speed of 80 km/h).

Luckily objects of the size of cat can be detected, but it is kind of expensive.

Just for you to know, there are 20,000 pieces of junk that is larger than softball.

Now the greatest risk is by the junk we cannot detect because it could destroy windows or so. Also the more stuff we put on the orbit, the more likely it is to collide with something.

By the way in 2007 China tried to get rid of one satellite using missile, what happened? They destroyed it adding 3,000 more pieces of debris on the orbit. WORTH A SHOT.

Right now there are only guidelines to dodge this debris but no real solution yet.

Dragallur

Check out this cool page that simulates what is flying above.

 

There is no centrifugal force

Hi,
why do you feel the push in carousel? Or when you are in car turning and you feel pushed on some person which can feel pretty awkward. This is all because of centrifugal force right?


YOU have been living in a lie

Your whole life was lie if you ever thought that there is something like centrifugal force.

So where is the problem? What causes us to fly from circle? There are three forces acting on you on carousel, gravity of Earth, the bench up so you do not fall through it and also towards the middle so you do not fly away. But still you feel the push from the circle, why if there is no force?

Your body wants to stay in the movement (it has some inertia) which is straight in direction and also in speed. This is Newton’s first law. But it does not because the bench goes in circle and you hold it so you go in circle too but your body does not want to do it so it would rather fly away in straight line which would be tangent to the movement.¬†

Above you can see that the line TP is what your movement would actually look like relative to the circle which is the carousel.

At every point of the movement you want to go tangent to the circle but you are holded by the force which has the tag of centripetal force. This is just a tag, all kinds of forces can be centripetal, gravity for orbits, friction of wheels for car in turn, ball on string or the bench of the carousel on which you are sitting.

Lesson: do not use the word centrifugal force anymore, it is not there and laws of physics would not work if it would be there.

Check out the video below showing when the speed gets way too big and the centripetal force simply is not able to hold it together anymore (here the centripetal force are the bonds holding the CD together):

Dragallur

Thanks my physics teacher!

Telescope of this generation

Hi,
this title is kind of weak, I know that, but I did not want to write “rusty, old piece of metal”. First because rusty could be a little bit misleading, rust only occurs when there is oxygen and there is only little of that in space, more accurately there is 1% of all the atoms in the Universe which is quite few tons but at the same time Hubble Space Telescope is flying in near vacuum when there are just a couple of hydrogen atoms per cubic meter, maybe in his lifespan he even touched few oxygen atoms. Second because he just does not deserve it. (Check out the post about James Webb Space Telescope)


His lifespan? Well it has been a long for such an instrument which are usually meant to work for much less years. For now the telescope has been working for 25 years, 9 months and 29 days. It is assumed that it might work for another 20 years or so, it could be even longer but it is slowing down and as I explained in post about orbits, it will eventually fall down and burn up in atmosphere. Not that this space telescope would be half immortal or so, but it was able to work for so many years because there were actually missions to repair some of its tools and power systems, otherwise it would not work by now [1].

When Hubble was launched and first images sent to NASA they were good, but not good enough which was because of the mirror. It was polished to a little bit wrong shape so they had to repair that. Before they did it NASA used some complicated image processing to get the best out of those pictures.

The repair itself was very complicated since replacing mirror was simply impossible and to bring the telescope back was too expensive. They solved it by making the same mistake but “of opposite direction” on another part of the telescope so it was totally canceled out, you can check out on the next picture to see how much it made a difference:

 

One of the images taken during the misson for some repair.

Pillars of creation, by Hubble

NASA even decided to borrow some of Hubble’s time for amateur astronomers, of course it was not easy to get that time but it was definitely worth it I am sure.

Hubble is not justing taking those beautiful pictures but it also helped to measure Hubbles constant on whole next level and also through his data we found out that the expansion of Universe is actually increasing, phenomenon which is not well understood but most people think that it is because of dark energy.

This is monstrosity, almost all of those bright points are galaxies, galaxies which we will most probably be never able to search through.

Hubble also helped with some observations of black holes and also as you can see above, Hubble made a whole new picture of the youngest parts of Universe, so extremely far away.

Depiction of progress in the detection of the early Universe

How far can we actually see?[2]

Dragallur

[1]Actually it is the first such thing in space that was repaired by humans which is actually pretty cool.

[2]Check out this post to read about red shift, the x axis on the picture.

All pictures from here and here

 

How do orbits work?

Hi,
I “came up” with this problem already some time ago but it is today that I am going to solve it here.


When you draw satellite above Earth and draw the forces that act on it you will see that there is only one force there (only one really important). It is the gravitational force of Earth. Why does not this satellite fall back you ask?

Well this is actually very interesting. The thing here is called orbital velocity. This is the velocity you need to orbit around Earth at particular distance.

So such a satellite orbits around Earth and you need the speed to be so big that gravity wont just pull it back but not too big so it does not fly away. I read somewhere great analogy: orbiting is just a falling without the crash. Take ISS for example. Why are there astronauts in “zero G” when they still receive 96% of Earths gravity? This is because the ISS is actually falling, kind of. It is falling around the Earth.. AROUND so it actually misses all the time. With extremely small drag and friction the ¬†satellites slow down just a little bit so they orbit for tens of years. For example ISS has to use its motors to get back on her height from Earth because otherwise it would fall down in some time.¬†

The closer you are to Earth, than the drag from atmosphere is greater so you must orbit at faster pace (+ the small amount of bigger gravity). Most satellites orbit in the low Earth orbit which is from 150-2000 kilometers or so.

Sometimes satellites need to be put away so they are moved on what is called satellite graveyard and they will orbit there for a long time. Or their path can be changed so they burn up in the atmosphere. The problem on Earths orbit is huge mess because of those years that we were just launching new and new satellites. This is a huge problem for the ones that are actually working and also for ISS because just a small piece of debris can do tremendous damage.

Dragallur

The picture