Category: Physics

The Edges of the Universe

… observed astrophysical black holes may be Einstein–Rosen bridges, each with a new universe inside that formed simultaneously with the black hole. Accordingly, our own Universe may be the interior of a black hole existing inside another universe.

— Poplawski, 2012: Radial motion into an Einstein–Rosen bridge (pdf) in Physics Letters B.

For some reason the Big Bang theory came up during a middle-school class discussion last week; specifically, the mind-bending question of what exactly was there just before and at the beginning of the universe. We also meandered into the question about what’s at the edge of the universe — and how can the universe have an edge where time and space end.

There really aren’t any satisfactory answers to these questions, especially not for middle schoolers. But it allowed me to talk about how science is really just the best explanations for the known observations. Unsatisfactory answers to these questions are why we have the scientific method.

A black hole passing in front of a galaxy acts as a giant lens. Image by Urbane Legend via Wikipedia.

To throw a little more mind-bending fuel on the fire, however, I’m going to show the class the article quoted above.

It’s an interesting example of how scientists see the universe through math. And how they strive to make sense of things they can’t see or touch.

Meteor Impact

The footage was taken [on February 14th] in the Urals, where over 200 were injured from the impact. The meteor was likely related to the asteroid 2012 DA14, which is scheduled to graze our planet [on the 15th] at 7.25 pm EST.

— Sullivan 2013: The Big Rock Heading Our Way on The Dish.

More details on Watts Up With That?

The meteor ended up hitting a factory. Photo from Twitter.com user @TimurKhorev via Watt’s Up With That.

Now think about the KT impact.

Update: More details and video at Sky and Telescope. Including this one:

Electrolysis with Universal Indicator

The universal pH indicator turns red for acids and blue for bases.

Ms. Wilson’s chemistry class did a beautiful electrolysis experiment by mixing a universal pH indicator into the salt solution. The indicator changes color based on how acidic or basic the solution is; we’ve used this behavior to show how blowing bubbles in water increases its acidity.

Changing colors of universal indicator show how blowing bubbles acidifies water (light green-second beaker) from neutral pH (dark green-third beaker) standard. For comparison, the first beaker (red) is acidified while the last beaker (blue) is made alkaline.

In this experiment, when electrodes (graphite pencil “leads”) are placed into salt (NaCl) water and connected to a battery, the sodium (Na) and chloride (Cl) split apart.

NaCl –> Na+ + Cl–

The positive sodium ion (Na+) migrates toward the negative electrode, where it gets an electron and precipitates on the electrode as a plating. This is called electroplating and is done to give fake gold and silver jewelry a nice outward appearance.

Similarly, the water (H2O) also dissociates into hydrogen (H+) and hydroxide (OH–) ions.

H2O –> H+ + OH–

Hydrogen bubbles forming at the negative electrode.

The positive hydrogen ions (H+) go toward the negative electrode where they get an electron from the battery and are liberated as hydrogen gas (when they bond to another hydrogen you get H2 gas). However, releasing the positive hydrogen ion, leaves behind hydroxide ions in the area around the positive electrode.

The opposite happens at the positive electrode, with hydrogen ions left behind in the solution.

Since acidity is a measure of the excess of hydrogen ions in solution (H+), the left behind hydrogen ions make the solution near the positive electrode acidic, which turns the indicator solution red. The OH– left near the negative electrode make the solution basic, which shows up as blue with the indicator.

If you gently shake the petri dish you end up with beautiful patterns like this:

Swirls.

And this:

After the electrodes have been disconnected.

Note: if the solution is mixed completely the hydrogen and hydroxide ions react with each other to make water again, the solution neutralizes, and becomes uniform again.

Note 2: This is an experiment that I should also do in physics. It should be interesting for students to see this experiment from two different perspectives to see how the subjects overlap.

Patterns in the Periodic Table

The rapid increase and slow decline of atomic radius repeats itself every 8 elements in the first 20 elements.

Why is the periodic table called the periodic table? Because of the periodic changes in the properties of the elements: there are patterns to the properties that repeat, time after time, as you go through the sequence of the elements. One key repetition, which affects the way different elements react, is in the electron configurations, however, other properties change as well. In fact, history of the periodic table
 is a story of scientists trying to figure out the properties of unknown elements (not to mention figuring out that there were undiscovered elements) based on what they knew about the periodicity of the known elements.

File: periodic-table-properties.xls

In this exercise, we look at four different properties that students need to be aware of: density, melting point, ionization energy, and electronegativity. I’ve compiled the data in this spreadsheet: periodic-table-properties.xls; and I handed out the first page, with the properties of the first 38 elements (periodic-table-properties.xls.pdf).

The repeating pattern in electronegativity shows up quite well in the first 20 elements.

I broke the class into pairs and had each pair graph one of the four sets of data. With 16 students that meant that we had a replicate of each graph, so I could use the redundancy as a quick check that they’d done them correctly.

The pattern with density is harder to discern, but it’s still there if you know where to look.

As they put drew their graphs I went around the classroom, paying special attention to the students working on ionization energy and electronegativity. Especially for the latter, I’d picked pairs who I figured would be able to get the graphs done quickly but would appreciate the extra challenge of figuring out what electronegativity actually is. This way, when everyone was done, the students could use their graphs to look for the patterns and explain what they’d found to the rest of the class.

The patterns of electronegativity rises across the first twenty elements.

Nuclear vs. Chemical Energy

This curious video advocates for a new type of nuclear reactor (that runs on thorium) over traditional uranium reactors and chemical fuels. In doing so it gives a useful, but quick, explanation of how energy is produced from these sources.

A Planet Being Formed

In the early stages of the formation of a solar system, dust in the nebula around a young star is attracted to each other because of their minute gravitational attraction to each other.

In the video below, accumulation of dust and gas creates a planet, probably a gas giant, that clears a swath of the solar nebula.

↬ ALMA (ESO/NAOJ/NRAO), M. Kornmesser (ESO) ↬ Space.com

The Science of Champagne Bubbles

This nice little video combines a bit of physics, chemistry, and biology as it discusses how bubbles form in champagne: the gas is carbon dioxide; carbon dioxide forms from the fermentation of sugars by yeast — it’s a byproduct of the reaction that produces alcohol; the bubbles form at tiny flaws or bubbles in the glass (so you can put in tiny flaws to control where the bubbles form); the bubbles rise because the gas is less dense than the liquid around it; and the bubbles expand as they rise because the pressure of the liquid becomes less and less the closer to the surface you are.

↬ The Dish