Common misconceptions about astronomy

[500]

24) Big Bang is a fact.

We know for sure that universe is expanding and that 13.7 billion years ago it was very hot and dense. But still it does not prove a Bing Bang. Big Bang theory does not work without inflation theory and in order to prove inflation we need to register gravity waves from it. Best way is to detect polarization of CMB by gravity waves. So far it was not detected thus Big Bang remains a theory.

25) Known universe started from the Big Bang.

According to current model, first was a "cold" Inflation stage expansion and only after that inflation field energy transformed into matter and heat, making it super dense and super hot, creating a Big Bang.

This misconception we can see in popular shows for example "How the universe works":

How the Universe Works S03E04 First Second HDTV XviD-AFG - Vidto (what they say from 10:46 is WRONG)

 

[500]

26) Earth rotates around its axis in 24 hours.

24 hours is length of a solar day (nychthemeron). However in addition to the rotation around axis there is additional factor which contributes a day change: thats rotation of planet around the sun - 1 day a year (if earth was not rotating at all we would have half year day and half year night). Earth rotates around its axis in 23 h 56 min and 4 sec. Additional 3 min and 56 sec are added because of the rotation around the sun.

27) Everest is highest point on Earth above its center.

The Earth does not have the shape of a perfect sphere. Instead it's diameter is greatest near the equator (due to planet rotation). Chimborazo mountain in Ecuador is located near the equator where Earth's diameter is greatest. This makes the summit of Chimborazo the highest point above the center of the Earth (2 km further than Everest).

 

[500]

28) Its hard to estimate the Universe age.

In fact all we need to calculate the approximate age of universe is Hubble's constant and school grade math.

Hubble constant = 67.8 km/s/Mpc
Mpc (Mega parsec) = 3.086*10^19 km

Now all we need is to divide range on speed and we will get time of expansion:
3.086*10^19 / 67.8 = 4.55*10^17 sec = 14.43 bln years.

Thats slightly more than actual age 13.82 bln years, but still very good estimate (less than 5% difference). Reason that our calculation is higher is because Hubble constant in the past was higher too.

 

[NP-complete]

nice thread

 

[500]

29) Stars are very effective source of energy.

Not really. For example, our Sun has power of 3,846·10^26 Wt and its mass is 1,9885·10^30 kg.

That means 100 kg of Sun radiates less than 0.02 Wt of energy.
For comparison 100 kg human radiates about 100 Wt of energy - 5000 times more!

nice thread

Thanks
.

 

[Hell hound]

29) Stars are very effective source of energy.

Not really. For example, our Sun has power of 3,846·10^26 Wt and its mass is 1,9885·10^30 kg.

That means 100 kg of Sun radiates less than 0.02 Wt of energy.
For comparison 100 kg human radiates about 100 Wt of energy - 5000 times more!


Thanks
.

now this is interesting.

 

[Talwar e Pakistan]

23) Water in our oceans came from comets.

Water in comets has much higher deuterium percent than water in our oceans. Thus it cant be from comets. Plus there is a strong evidence that Earth had oceans before the comet bombardment.

Then where did oceans come from?

 

[XenoEnsi-14]

Then where did oceans come from?

Under the crust, Ringwoodite and hydroxide in the mantle.

 

[500]

Then where did oceans come from?

No one knows for sure. Apparently water existed on Earth since its formation. According to one theory during creation of the Earth Jupiter migrated close to Mars and threw water into the Inner Solar System. Later that water was taken out to Earth surface by volcanoes.

 

[risingsinga]

@500 Can you please provide references to the original pages/source from where you get this information?

 

[500]

@500 Can you please provide references to the original pages/source from where you get this information?

Its based on my own knowledge. I studied physics and interested in astronomy (especially cosmology). You can find references by googling quite easily I guess. Anything specific that interests u?

 

[risingsinga]

Its based on my own knowledge. I studied physics and interested in astronomy (especially cosmology). You can find references by googling quite easily I guess. Anything specific that interests u?

Oh I see. I have some different opinion/information.

 

[Jungibaaz]

Great stuff OP. I consider myself a space enthusiast but a few of these even I learnt something new about.

 

[500]

30) Big bang happened because of huge pressure in the beginning of the universe.

This misconception is related to #1 since explosions happen because of huge pressure created by rapidly burning explosive materials. And early universe indeed had a huge pressure. However regular explosions happen because of the difference of pressures: huge pressure inside a shell and little pressure outside. But in universe there is no outside. It had a huge pressure everywhere so there is no difference of pressures which could cause expansion.

Ironically according to General Theory or Relativity, huge pressure actually increases gravitation and thus slows down the expansion.

Then what pushed the expansion of the universe? Well we dont know for sure. Commonly accepted is Inflation Theory, which says that it was super dense vacuum (or super dense pseudo vacuum), which produced negative pressure and pushed the expansion. Then after very very short in time, but very very huge expansion, the energy of super dense vacuum transformed into a regular matter as I noted in #25.

You may ask now what the heck is "super dense vacuum". Well according to quantum theory vacuum is not exactly empty. There are always some virtual particles which born and annihilate all the time. Its called "boiling of vacuum". Boiling can be different in its insensitivity. Thus vacuum has some energy, which is usually very very low. However under some extreme conditions vacuum may have a huge energy. Thats what is called "dense (or sometimes heavy) vacuum".

Oh I see. I have some different opinion/information.

Can you tell me specific what about? Probably we can solve it together. I am very sure about everything I posted here.

 

[risingsinga]

Can you tell me specific what about? Probably we can solve it together. I am very sure about everything I posted here.

Thanks. The radius of the visible universe is estimated to be 46 billion years
29) Dividing by the surface won't do the justice the total influx of the solar energy is responsible for the life on the planet Earth.