When The Sun Goes Dark: 5 Questions Answered About The Solar Eclipse


Published:

NASA’s projection of the August 21 solar eclipse.

© NASA

Editor’s note: A total solar eclipse will be visible across the U.S. on Monday, August 21. Shannon Schmoll, director of the Abrams Planetarium at Michigan State University, explains why and how it happens, and what we can learn from an eclipse.

How do we know when an eclipse is going to happen? How do we know in advance where it will be visible?

Solar eclipses happen when our view of the sun is blocked by the moon. When the moon lines up between the sun and Earth, the moon will cast a shadow onto Earth. This is what we on the ground observe as a solar eclipse.

We know when they’ll happen because over centuries astronomers have measured very precisely the motions of the Earth, moon and sun, including their orbital shapes, how the orbits precess and other parameters. With those data about the moon – and similar information about the Earth’s orbit around the sun – we can make mathematical models of their movements in relation to each other. Using those equations, we can calculate tables of data that can predict what we will see on Earth, depending on location, during an eclipse as well as when they will happen and how long they last. (The next major solar eclipses over the U.S. will be in 2023 and 2024.)

The path of the eclipse on August 21. NASA

How often do eclipses happen?

A solar eclipse happens, on average, a couple times a year. The moon passes between the Earth and sun every 29 days, a time we call the “new moon” – when the moon is not visible in Earth’s nighttime sky. However, the moon’s orbit and the sun’s path in our sky don’t match up exactly, so at most of those new moon events, the moon appears above or below the sun.

The blue line shows the ecliptic, the path the sun appears to take in our sky as viewed from Earth. The white line shows the moon’s orbit. For eclipses to happen, both the sun and the moon need to be within the area marked with yellow brackets. John French, Abrams Planetarium, CC BY-ND

Twice a year, though, there is a period where the moon and the sun line up with Earth – astronomers call this an eclipse season. It lasts about 34 days, long enough for the moon to complete a full orbit (and then some) of the Earth. During each eclipse season, there are at least two eclipses visible from some parts of the Earth. At the full moon, there will be a lunar eclipse, when the moon passes directly behind the Earth, resulting in a darker, reddish-colored moon. And at the new moon, there will be a solar eclipse, when the sun is blocked by the moon.

Can we learn anything from eclipse events, or are they really just oddities that happen in nature?

We can definitely learn things from eclipses. The outermost layer of the sun, known as the corona, is difficult to study because it’s less bright than the rest of the sun – so we have trouble seeing it amid the rest of the sun’s brightness.

The blue line shows the ecliptic, the path the sun appears to take in our sky as viewed from Earth. The white line shows the moon’s orbit. For eclipses to happen, both the sun and the moon need to be within the area marked with yellow brackets. John French, Abrams Planetarium, CC BY-ND When the moon blocks the sun, we can see the corona, the famous visual of the halo of light around the dark disk of the moon. Currently astronomers study this by creating an artificial eclipse with a mask built into special instruments on telescopes called coronagraphs. This is great, but doesn’t allow the best pictures. Eclipses give scientists opportunities to get more data to study the corona in depth.

We can also learn about Earth itself. In an area affected by an eclipse, the darkening of the sun leads to a sudden drop in temperature. NASA-funded studies during this eclipse will look at the effects from the eclipse on our atmosphere as well as what happens on land. Previous studies observed animal behavior during an eclipse in 2001 and noted some animals went through their night routines as the sun disappeared while others became nervous.

And we can learn about the whole universe. Less than 100 years ago, an eclipse proved a prediction Albert Einstein had made about gravity. That success helped make him a household name. In his general theory of relativity, Einstein had predicted that gravity could bend the path of light. The effect he predicted was very slight, so it would best be viewed as the light passed a very large celestial body as part of its travels across a very long distance of space.

Sir Arthur Eddington, an astronomer who helped further the study of general relativity and whose work is a major piece of our modern understanding of stars and black holes, used the darkness provided by a solar eclipse to look at the position of the stars’ light during the day, when it passed the sun. He then compared those positions to their known positions at night. He saw that the gravity of the sun had bent the path – exactly as, and in the precise amount that, Einstein had predicted.

How weird is it that the moon can basically exactly block out the sun?

It is very unusual that the moon and the sun just happen to be at the right distances and sizes to appear to have the same size in our sky. This allows the moon to perfectly block the sun’s disk, while also showing us the corona. Venus and Mercury, for instance, can also pass in front of the sun from our perspective. However, they appear as small specks moving across the sun.

Venus appears as a small dot in the upper left as it passes between the sun and Earth in 2012. NASA

What would someone standing on the moon see happen on Earth? Would Earth get dark?

If you were on the moon, you would be able to see the effects of the solar eclipse on Earth only if you were standing on the moon’s night side, the side facing the Earth. You would see a round shadow cast onto the Earth. This particular eclipse will first hit the Pacific Ocean, then move into Oregon, cross the U.S. to South Carolina and end in the Atlantic Ocean. This path the shadow takes is called the path of totality.

Protect your eyes when viewing a solar eclipse:

Looking directly at the sun can severely damage your eyes. To watch the eclipse while still protecting your eyesight, do at least one of three things, whether you are in the path of totality or only viewing a partial eclipse.

1. Purchase eclipse glasses from reputable stores such as a local planetarium or science center.

2. Use welder's glass – be sure to get darkness number 14.

3. Build a device to display a projection of the sun's image.

4. Don't remove your eye protection unless you're certain you're looking at the sun during the short period when it's completely eclipsed by the moon – and never remove it if you're in an area where only a partial eclipse is viewable.

Shannon Schmoll has a PhD in astronomy and science education. She is the director of the Abrams Planetarium at Michigan State University. She is guiding the planetarium in the development of engaging and interactive astronomy programming including full dome shows and exhibits and building partnerships with various groups on the MSU campus and the greater Lansing and Michigan communities.

This article was republished from The Conversation.

Edit Module
Edit ModuleShow Tags
Edit Module Edit ModuleShow Tags

Daily Astrology

May 25, 2018

Take notes as thoughts and feelings are unusually profound. An early morning trine between Jupiter and Neptune offers a rich communion between minds and hearts. Mental Mercury’s ensuing trine with Pluto deepens curiosity and gives insights into life’s…
Edit ModuleShow Tags

Alternative Health Directory

Browse all listings »

Edit ModuleShow Tags
Edit ModuleShow Tags

Calendar

May 2018

Spend a day in conversation with angels! Heal and empower yourself with the energy of angels. You will learn the special healing gift that each of nine healing angels brings and how this relates...

Cost: $111

Where:
Be Well Studios
3358 White Mountain Highway
North Conway, NH  03860
View map »


Sponsor: Pathway Of Joy
Telephone: 207-329-7192
Contact Name: Linda Huitt
Website »

More information

Do you desire more connection and intimacy? Do you want to increase the quality of your intimacy? Does fear of rejection, misinterpretation or expectations hold you back from initiating?...

Cost: $187 per person

Where:
Watertown Center for Healing Arts
22 Mount Auburn St
Watertown, MA
View map »


Sponsor: Conscious Intimacy
Telephone: 415-244-1652
Contact Name: Brynn Bishop
Website »

More information

With Dido Nydick A Restorative Yoga practice to experience relaxation for well-being. Each class will consist of a reclining pose sequence designed to restore the nervous system and help release...

Cost: $25

Where:
YogaLife Institute of NH
6 Chestnut Street
Lower Level
Exeter, NH  03833
View map »


Sponsor: YogaLife Institute of NH
Telephone: 603-867-3969
Contact Name: Alice Bentley
Website »

More information

Sunday yoga is back! Hatha Yoga with meditation to get you ready to tackle your spring intentions. Sign up for series or drop in. 

Cost: $75/5 classes; drop in $17.00

Where:
Dragonfly Wellness Center
176 Jackson Rd
Devens, MA
View map »


Sponsor: Dragonfly Wellness Center
Telephone: 978-227-8297
Contact Name: Anita Perry
Website »

More information

Show More...
Show Less...
No Events

Feel the bliss of opening your spine, while being totally supported and meticulously aligned. Great for sciatica and low back pain! Classes also held Saturday mornings.

Cost: $18 drop in

Where:
Bliss Through Yoga
484 Bedford St
East Bridgewater, MA  02333
View map »


Sponsor: Bliss Through Yoga
Telephone: 508-331-3564
Contact Name: Janice
Website »

More information

8 Week Mindfulness Based Stress Reduction Course with Erin Woo Tuesdays, May 1 - June 19, 6–8:30 pm *Includes an all day retreat on Saturday, June 9 from 9 am - 4 pm Come explore the...

Cost: $290

Where:
Balance Bethlehem
2087 Main Street
Bethlehem, NH  03574
View map »


Sponsor: Balance Bethlehem
Telephone: 603-869-2125
Website »

More information

Show More...
Show Less...
No Events

YogaLife studio would like to offer this opportunity to slow it down, step back, notice your breath and sit quietly in community. Join us Thursdays from 5:40-6:30 PM. No Yoga...

Cost: Free

Where:
YogaLife Institute
6 Chestnut Street
Suite A
Exeter, MA  03833
View map »


Telephone: 603-969-8968
Website »

More information

Show More...
Show Less...

May 25 - 27 The heroic and shamanic journeys weave throughout human history. Each requires the protagonist to journey into another order of reality, a landscape of magic and mystery…...

Cost: $325 – includes food

Where:
Putney, VT  05346


Sponsor: Circles of Air and Stone
Telephone: 802-387-6624
Contact Name: Sparrow Hart
Website »

More information

Designed to prepare individuals who are interested in helping themselves and others in a rewarding career as a Professional Certified Hypnotist/Hypnotherapist. Live demonstration, supervised...

Cost: $1995 ppd. (Early Bird by 5/14 - $1795)

Where:
Women of Wisdom
118 Washington Street
North Easton, MA  02356
View map »


Sponsor: Women of Wisdom
Telephone: 508-230-3680
Contact Name: Women of Wisdom
Website »

More information

Dominic Boag is one of the UK’s finest psychic mediums. Dominic has been taking his events to audiences across Scotland. He is the Scottish Sun’s Psychic and writes his own column named...

Where:
American Legion Post 440
295 California St.
Newton, MA  02458
View map »


Sponsor: Greater Boston Church of Spiritualism
Telephone: 617-861-1440
Website »

More information

May 25 - 28, 2018 Save the date! Four days of learning, earth healing, music, meditation, dance and delicious organic food! All are welcome!

Where:
Old King Farm
567 Money Hole Road
Benson, VT  05743
View map »


Telephone: 802-537-3460
Website »

More information

Show More...
Show Less...
No Events
Edit ModuleShow Tags
Edit Module Edit ModuleShow Tags