Category: earth

Ask Ethan: How Do We Know The Age Of The Solar…

Ask Ethan: How Do We Know The Age Of The Solar System?

“How do we know the age of our solar system? […] I have a loose grasp on the concept of dating the time elapsed since a rock was liquid, but 4.5 Billion years is roughly how long ago Theia hit proto-Earth liquefying a massive amount of everything. […] How do we know we’re actually dating the solar system and not just finding dozens of ways to date the Theia collision?”

You’ve probably heard the estimates before: that the Earth, the Sun, and the rest of the Solar System are all about 4.5 or 4.6 billion years old. But why be so imprecise? We don’t have to be! In fact, we know that there are slight variations, and based on the fact that we think that the Earth-Moon system formed from a giant impact tens of millions of years after the rest of the Solar System did, we shouldn’t get the same answer for everything! It turns out that we’ve now advanced to the point where we can actually give answers that are extremely accurate: the Earth-Moon system should be 4.51 billion years old; the oldest meteorites show an age for the rest of the Solar System of 4.568 billion years, and the Sun may be a little older at 4.6 billion years.

How do we know? The science of radioactive decay holds the answer, and it’s a lot more complex, but a lot more well-understood, than you might think!

Remnants Of Our Solar System’s Formation Found…

Remnants Of Our Solar System’s Formation Found In Our Interplanetary Dust

“Our naive picture of a disk that gets very hot, fragments, and cools to then form planets may be hopelessly oversimplified. Instead, we’ve learned that it may actually be cold, outer material that holds the key to our planetary backyard. If the conclusions of the Ishii et al. paper stand the test of time, we may have just revolutionized our understanding of how all planetary systems come into being.”

How did Earth (and the other planets) form? According to conventional wisdom, a molecular cloud collapsed, formed a protoplanetary disk, funneled material into the center, and gave birth to a star. This star then blew off the gas and light elements from the inner Solar System, with the planets we have today representing the survivors from these hot, early stages. Only, what if that picture weren’t correct after all? What if the material that gave rise to our (and other) worlds wasn’t forged in an inferno, but in a colder, more distant environment that only fell into the inner reaches at a later time?

The way to decide would be to identify and examine material left over from these early stages of Solar System formation in enough detail. For the first time, we’ve done exactly that. Don’t miss the results!

Could We Create A Bottomless Pit On Earth?

Could We Create A Bottomless Pit On Earth?

“A round-trip journey, from the North Pole to just shy of the South Pole and back to the North Pole again, all through the Earth’s center, should take just a whisker under 90 minutes. Under ideal conditions:

* creating a vacuum,
* straight through the Earth’s rotational axis,
* starting with no tangential velocity,
* devoid of any type of air resistance and subject only to gravitational forces,

you’d wind up right back where you started just 90 minutes later: roughly the same time it takes the international space station to orbit the Earth. So long as you brought an oxygen supply with you, you’d be no worse for the wear.”

From tourist traps to Alice in Wonderland to modern entertainment like Gravity Falls, bottomless pits are tropes that hardly seem physically possible. Sure, you can always envision a thought experiment, but that doesn’t mean you could actually build one. Despite the engineering challenges and the enormous expense that would be associated with such a project, this one turns out to be physically plausible with not-too-distant-future technology. There are a number of obstacles we’d have to overcome, including the Earth’s rotation, drilling a shaft clear through the planet, and stabilizing a passenger against the heat and radioactivity of the natural interior of our world. But if we could do it, and not get stuck at the center, we’d come back to where we started just 90 minutes later.

Here’s the story behind how to create and successfully use a bottomless pit here on Earth!

Earth’s rotation is slowing slightly with time

Earth’s rotation is slowing slightly with time:

“In the year 1820, a rotation took exactly 24 hours, or 86,400
standard seconds. Since 1820, the mean solar day has increased by about
2.5 milliseconds.”

“At the time of the dinosaurs, Earth completed one rotation in
about 23 hours,” says MacMillan, who is a member of the VLBI team at
NASA Goddard.

* How can the moon slow down the earth ?

image

Are the heavens moving or are we?

image

In the previous series of posts, we discussed about the key role that a rotating earth plays in space shuttle launches and quickly skimmed through why the earth began to rotate in the first place.

But in the 21st century, there are many experiments  (Coriolis effect,  Foucault’s pendulum ,etc, etc) that you can do to convince yourself that the Earth is indeed rotating.

image

                                             ISS Live Stream

But back in the days of Galileo it was still debatable whether Earth was rotating or not. 

Why does a ball thrown straight up in the air fall to the same place on the ground ?

image

One
of the profound Aristotelian arguments against the rotation of the
Earth was that if the Earth were rotating, a thrown ball/arrow would not
land in the same place that it was thrown.

image

This was believed so
because, by the time the projectile traverses its path the Earth would
have moved by a certain distance. Hence, the ball would never land at
the same place it was thrown.

#############################################################

Take a second to think about this. Can you come up with an argument against this rationale ?

##############################################################


Here
is an excellent argument given by Galileo in favor of the rotation of
the Earth and why things would still fall to the same place even if the
Earth were rotating:

In replying to this, those who make the earth movable answer that the canon and the ball which are on the earth share its motion or rather that all of them together have the same motion naturally.

Therefore the ball does not start from rest at all but to its motion about the center joins one of projection upward which neither removes not impedes the former.

You
will see the same thing by making the experiment on a ship with a ball
thrown perpendicularly upward from a catapult. It will return to the
same place whether the ship is moving or standing still

The profundity of this argument is that, the very same principle that ‘ball does not start from rest at all  but with velocity of the earth’ is used by space shuttles to reach orbital velocity with lesser fuel consumption.

image

But despite Galileo’s argument, it was still believed for a long time that it were the heavens that moved and not the earth.

For
God hath established the world which shall not be moved in spite of
contrary reasons because they are clearly not conclusive persuasions.

image

fuckyeahphysica: The Tale of Earth and it’s sister Theia. Have…

fuckyeahphysica:

The Tale of Earth and it’s sister Theia.

Have you found it weird that the earth’s axis is tilted by 23.5 degrees and wondered what led to this? Wait, Where did the moon come from?

Well, Here’s what scientists have theorized.

The Giant Impact Hypothesis

Theia, a mars sized planet collided ( it glanced and thankfully did not collide head on, else it would have destroyed earth ) with the Earth around 4.553 billion years ago.

image

Theia’s debris gathered together around Earth to form what we now call- The Moon.

image

The collision between the early earth and Theia was so immense that
it tilted the axis of rotation of the early earth by 23.5 degrees.

And
it remains tilted so that way even today!!

image

Why do they believe in this hypothesis ?

Scientists have a very good reason to believe in the Giant Impact Hypothesis:

  • Earth’s spin and the Moon’s orbit have similar orientations.
  • Moon samples indicate that the Moon once had a molten surface.
  • The Moon has a relatively small iron core.
  • The Moon has a lower density than Earth.
  • Evidence exists of similar collisions in other star systems (that result in debris disks).
  • Giant collisions are consistent with the leading theories of the formation of the solar system.
  • The stable-isotope ratios of lunar and terrestrial rock are identical, implying a common origin
image

Have a good day !

PC: sarice,

Now not only do we now have an understanding of why the earth is spinning but also why the axis of rotation is inclined by 23.5 degrees.

Stay tuned for more..

Why did the Earth start spinning?

We have been discussing about the rotation of the Earth in the past couple of posts but lets take a second to understand why the earth is rotating in the first place.

Here is a quick summary:

Our Solar System formed about 4.6 billion years ago when a huge cloud
of gas and dust started to collapse under its own gravity.

image
image

As the cloud collapsed, it started to spin. Some of the material
within this cloud gathered into swirling eddies and eventually formed
into planets. As the planets formed, they kept this spinning motion.

image

As material gathered in more closely to form a planet, like Earth, the
material spun faster. This is similar to what you see when skaters pull in their arms and spin
faster.

And as a result since there are no forces are acting on Earth to slow it down, it continues to spin to this day. **

** not entirely true as we shall explore soon

Previous posts:

The shape of the Earth is an oblate spheroid: A visual demo

How does earth’s rotation affect space shuttle launches ?

Shape of Earth is an oblate spheroidAs you can see from this…

Shape of Earth is an oblate spheroid

As you can see from this dramatic demonstration, the consequence of imparting a rotational velocity to an object is the flattening of object at the poles.

The rotational velocity of Earth is a staggering 1,674.4 km/h 
and as a result  bulges at the center by a tiny fraction, as is evident from the following image:

image

The 19 Small Ways That NASA Will Try To Save T…

The 19 Small Ways That NASA Will Try To Save The Earth

“The key to adapting to a changing world, not just as individuals but as the human race, requires us to use the best tools and information at our disposal. That means paying attention to what the Earth is doing, both naturally and artificially, and using the best data available to drive our policy decisions. These 19 future missions represent the short-and-medium-term roadmap for NASA Earth Science, and every one of these missions is currently slated to go forward, as long as there aren’t unexpected cuts in the future. This Earth Day, don’t just celebrate our planet only to forget about it; keep in mind what we’re doing to learn about our world and why it’s valuable. This planet is the only Earth we’ve got, and it’s up to us to be good stewards of this world. Without quality scientific information on which to base good decisions, from a global perspective, we’d be nothing more than animals.”

When people think of NASA, they think of spaceflight, of technology, and of science. But most of the science they think of is astrophysics or planetary science, not Earth Science. Well, that’s foolish; Earth Science is one of the Science Mission Directorate’s four major realms of study, as we can learn things about our world from the air and from space that we cannot hope to learn from surface investigations alone. Over the coming months and years, NASA has 19 new missions slated to help better investigate and understand the Earth, including our weather, climate, pollution, CO2, temperature, and more. If you care about accurate information, you’ll start to understand why all of these missions are indispensable to a scientifically-minded society.

Come learn about the 19 small ways, from missions small to large, that NASA’s Earth Science directorate will try and help save the Earth.

OKay.. THis might seem like a stupid question.. But why doesn’t the earth spiral into the sun ? Like why is orbiting it ?

image

In a recent post we demonstrated using the Newton’s cannon thought experiment that:

ISS and other satellites are always falling, but they are falling in Orbit

And this applies to planetary bodies too: Earth is always trying to fall into the sun, but it keeps falling in an orbit instead

But where did the initial velocity for the earth come from ?

Well, to answer that question one needs to go back 4.6 Billion years ago and look at the formation of the solar system.

image

And if you like numerical simulation and are wondering how could a spinning cloud of gas eventually form planets, take a look at the following video and its source paper.

Thanks for asking!