下載App 希平方
攻其不背
App 開放下載中
下載App 希平方
攻其不背
App 開放下載中
IE版本不足
您的瀏覽器停止支援了😢使用最新 Edge 瀏覽器或點選連結下載 Google Chrome 瀏覽器 前往下載

免費註冊
! 這組帳號已經註冊過了
Email 帳號
密碼請填入 6 位數以上密碼
已經有帳號了?
忘記密碼
! 這組帳號已經註冊過了
您的 Email
請輸入您註冊時填寫的 Email,
我們將會寄送設定新密碼的連結給您。
寄信了!請到信箱打開密碼連結信
密碼信已寄至
沒有收到信嗎?
如果您尚未收到信,請前往垃圾郵件查看,謝謝!

恭喜您註冊成功!

查看會員功能

註冊未完成

《HOPE English 希平方》服務條款關於個人資料收集與使用之規定

隱私權政策
上次更新日期:2014-12-30

希平方 為一英文學習平台,我們每天固定上傳優質且豐富的影片內容,讓您不但能以有趣的方式學習英文,還能增加內涵,豐富知識。我們非常注重您的隱私,以下說明為當您使用我們平台時,我們如何收集、使用、揭露、轉移及儲存你的資料。請您花一些時間熟讀我們的隱私權做法,我們歡迎您的任何疑問或意見,提供我們將產品、服務、內容、廣告做得更好。

本政策涵蓋的內容包括:希平方學英文 如何處理蒐集或收到的個人資料。
本隱私權保護政策只適用於: 希平方學英文 平台,不適用於非 希平方學英文 平台所有或控制的公司,也不適用於非 希平方學英文 僱用或管理之人。

個人資料的收集與使用
當您註冊 希平方學英文 平台時,我們會詢問您姓名、電子郵件、出生日期、職位、行業及個人興趣等資料。在您註冊完 希平方學英文 帳號並登入我們的服務後,我們就能辨認您的身分,讓您使用更完整的服務,或參加相關宣傳、優惠及贈獎活動。希平方學英文 也可能從商業夥伴或其他公司處取得您的個人資料,並將這些資料與 希平方學英文 所擁有的您的個人資料相結合。

我們所收集的個人資料, 將用於通知您有關 希平方學英文 最新產品公告、軟體更新,以及即將發生的事件,也可用以協助改進我們的服務。

我們也可能使用個人資料為內部用途。例如:稽核、資料分析、研究等,以改進 希平方公司 產品、服務及客戶溝通。

瀏覽資料的收集與使用
希平方學英文 自動接收並記錄您電腦和瀏覽器上的資料,包括 IP 位址、希平方學英文 cookie 中的資料、軟體和硬體屬性以及您瀏覽的網頁紀錄。

隱私權政策修訂
我們會不定時修正與變更《隱私權政策》,不會在未經您明確同意的情況下,縮減本《隱私權政策》賦予您的權利。隱私權政策變更時一律會在本頁發佈;如果屬於重大變更,我們會提供更明顯的通知 (包括某些服務會以電子郵件通知隱私權政策的變更)。我們還會將本《隱私權政策》的舊版加以封存,方便您回顧。

服務條款
歡迎您加入看 ”希平方學英文”
上次更新日期:2013-09-09

歡迎您加入看 ”希平方學英文”
感謝您使用我們的產品和服務(以下簡稱「本服務」),本服務是由 希平方學英文 所提供。
本服務條款訂立的目的,是為了保護會員以及所有使用者(以下稱會員)的權益,並構成會員與本服務提供者之間的契約,在使用者完成註冊手續前,應詳細閱讀本服務條款之全部條文,一旦您按下「註冊」按鈕,即表示您已知悉、並完全同意本服務條款的所有約定。如您是法律上之無行為能力人或限制行為能力人(如未滿二十歲之未成年人),則您在加入會員前,請將本服務條款交由您的法定代理人(如父母、輔助人或監護人)閱讀,並得到其同意,您才可註冊及使用 希平方學英文 所提供之會員服務。當您開始使用 希平方學英文 所提供之會員服務時,則表示您的法定代理人(如父母、輔助人或監護人)已經閱讀、了解並同意本服務條款。 我們可能會修改本條款或適用於本服務之任何額外條款,以(例如)反映法律之變更或本服務之變動。您應定期查閱本條款內容。這些條款如有修訂,我們會在本網頁發佈通知。變更不會回溯適用,並將於公布變更起十四天或更長時間後方始生效。不過,針對本服務新功能的變更,或基於法律理由而為之變更,將立即生效。如果您不同意本服務之修訂條款,則請停止使用該本服務。

第三人網站的連結 本服務或協力廠商可能會提供連結至其他網站或網路資源的連結。您可能會因此連結至其他業者經營的網站,但不表示希平方學英文與該等業者有任何關係。其他業者經營的網站均由各該業者自行負責,不屬希平方學英文控制及負責範圍之內。

兒童及青少年之保護 兒童及青少年上網已經成為無可避免之趨勢,使用網際網路獲取知識更可以培養子女的成熟度與競爭能力。然而網路上的確存有不適宜兒童及青少年接受的訊息,例如色情與暴力的訊息,兒童及青少年有可能因此受到心靈與肉體上的傷害。因此,為確保兒童及青少年使用網路的安全,並避免隱私權受到侵犯,家長(或監護人)應先檢閱各該網站是否有保護個人資料的「隱私權政策」,再決定是否同意提出相關的個人資料;並應持續叮嚀兒童及青少年不可洩漏自己或家人的任何資料(包括姓名、地址、電話、電子郵件信箱、照片、信用卡號等)給任何人。

為了維護 希平方學英文 網站安全,我們需要您的協助:

您承諾絕不為任何非法目的或以任何非法方式使用本服務,並承諾遵守中華民國相關法規及一切使用網際網路之國際慣例。您若係中華民國以外之使用者,並同意遵守所屬國家或地域之法令。您同意並保證不得利用本服務從事侵害他人權益或違法之行為,包括但不限於:
A. 侵害他人名譽、隱私權、營業秘密、商標權、著作權、專利權、其他智慧財產權及其他權利;
B. 違反依法律或契約所應負之保密義務;
C. 冒用他人名義使用本服務;
D. 上載、張貼、傳輸或散佈任何含有電腦病毒或任何對電腦軟、硬體產生中斷、破壞或限制功能之程式碼之資料;
E. 干擾或中斷本服務或伺服器或連結本服務之網路,或不遵守連結至本服務之相關需求、程序、政策或規則等,包括但不限於:使用任何設備、軟體或刻意規避看 希平方學英文 - 看 YouTube 學英文 之排除自動搜尋之標頭 (robot exclusion headers);

服務中斷或暫停
本公司將以合理之方式及技術,維護會員服務之正常運作,但有時仍會有無法預期的因素導致服務中斷或故障等現象,可能將造成您使用上的不便、資料喪失、錯誤、遭人篡改或其他經濟上損失等情形。建議您於使用本服務時宜自行採取防護措施。 希平方學英文 對於您因使用(或無法使用)本服務而造成的損害,除故意或重大過失外,不負任何賠償責任。

版權宣告
上次更新日期:2013-09-16

希平方學英文 內所有資料之著作權、所有權與智慧財產權,包括翻譯內容、程式與軟體均為 希平方學英文 所有,須經希平方學英文同意合法才得以使用。
希平方學英文歡迎你分享網站連結、單字、片語、佳句,使用時須標明出處,並遵守下列原則:

  • 禁止用於獲取個人或團體利益,或從事未經 希平方學英文 事前授權的商業行為
  • 禁止用於政黨或政治宣傳,或暗示有支持某位候選人
  • 禁止用於非希平方學英文認可的產品或政策建議
  • 禁止公佈或傳送任何誹謗、侮辱、具威脅性、攻擊性、不雅、猥褻、不實、色情、暴力、違反公共秩序或善良風俗或其他不法之文字、圖片或任何形式的檔案
  • 禁止侵害或毀損希平方學英文或他人名譽、隱私權、營業秘密、商標權、著作權、專利權、其他智慧財產權及其他權利、違反法律或契約所應付支保密義務
  • 嚴禁謊稱希平方學英文辦公室、職員、代理人或發言人的言論背書,或作為募款的用途

網站連結
歡迎您分享 希平方學英文 網站連結,與您的朋友一起學習英文。

抱歉傳送失敗!

不明原因問題造成傳送失敗,請儘速與我們聯繫!
希平方 x ICRT

「Dustin Schroeder:透視南極冰蓋」- How We Look Kilometers below the Antarctic Ice Sheet

觀看次數:2178  • 

框選或點兩下字幕可以直接查字典喔!

I'm a radio glaciologist. That means that I use radar to study glaciers and ice sheets. And like most glaciologists right now, I'm working on the problem of estimating how much the ice is going to contribute to sea level rise in the future. So today, I want to talk to you about why it's so hard to put good numbers on sea level rise, and why I believe that by changing the way we think about radar technology and earth-science education, we can get much better at it.

When most scientists talk about sea level rise, they show a plot like this. This is produced using ice sheet and climate models. On the right, you can see the range of sea level predicted by these models over the next 100 years. For context, this is current sea level, and this is the sea level above which more than 4 million people could be vulnerable to displacement. So in terms of planning, the uncertainty in this plot is already large.

However, beyond that, this plot comes with the asterisk and the caveat, "... unless the West Antarctic Ice Sheet collapses." And in that case, we would be talking about dramatically higher numbers. They'd literally be off the chart. And the reason we should take that possibility seriously is that we know from the geologic history of the Earth that there were periods in its history when sea level rose much more quickly than today. And right now, we cannot rule out the possibility of that happening in the future. So why can't we say with confidence whether or not a significant portion of a continent-scale ice sheet will or will not collapse?

Well, in order to do that, we need models that we know include all of the processes, conditions and physics that would be involved in a collapse like that. And that's hard to know, because those processes and conditions are taking place beneath kilometers of ice, and satellites, like the one that produced this image, are blind to observe them. In fact, we have much more comprehensive observations of the surface of Mars than we do of what's beneath the Antarctic ice sheet. And this is even more challenging in that we need these observations at a gigantic scale in both space and time.

In terms of space, this is a continent. And in the same way that in North America, the Rocky Mountains, Everglades and Great Lakes regions are very distinct, so are the subsurface regions of Antarctica. And in terms of time, we now know that ice sheets not only evolve over the timescale of millennia and centuries, they're also changing over the scale of years and days. So what we want is observations beneath kilometers of ice at the scale of a continent, and we want them all the time.

So how do we do this? Well, we're not totally blind to the subsurface. I said in the beginning that I was a radio glaciologist, and the reason that that's a thing is that airborne ice-penetrating radar is the main tool we have to see inside of ice sheets. So most of the data used by my group is collected by airplanes like this World War II-era DC-3 that actually fought in the Battle of the Bulge. You can see the antennas underneath the wing. These are used to transmit radar signals down into the ice. And the echos that come back contain information about what's happening inside and beneath the ice sheet. While this is happening, scientists and engineers are on the airplane for eight hours at a stretch, making sure that the radar's working. And I think this is actually a misconception about this type of fieldwork, where people imagine scientists peering out the window, contemplating the landscape, its geologic context and the fate of the ice sheets. We actually had a guy from the BBC's "Frozen Planet" on one of these flights. And he spent, like, hours videotaping us turn knobs.

And I was actually watching the series years later with my wife, and a scene like this came up, and I commented on how beautiful it was. And she said, "Weren't you on that flight?"

I said, "Yeah, but I was looking at a computer screen."

So when you think about this type of fieldwork, don't think about images like this. Think about images like this.

This is a radargram, which is a vertical profile through the ice sheet, kind of like a slice of cake. The bright layer on the top is the surface of the ice sheet, the bright layer on the bottom is the bedrock of the continent itself, and the layers in between are kind of like tree rings, in that they contain information about the history of the ice sheet. And it's amazing that this works this well. The ground-penetrating radars that are used to investigate infrastructures of roads or detect land mines struggle to get through a few meters of earth. And here we're peering through three kilometers of ice. And there are sophisticated, interesting, electromagnetic reasons for that, but let's say for now that ice is basically the perfect target for radar, and radar is basically the perfect tool to study ice sheets.

These are the flight lines of most of the modern airborne radar-sounding profiles collected over Antarctica. This is the result of heroic efforts over decades by teams from a variety of countries and international collaborations. And when you put those together, you get an image like this, which is what the continent of Antarctica would look like without all the ice on top. And you can really see the diversity of the continent in an image like this. The red features are volcanoes or mountains; the areas that are blue would be open ocean if the ice sheet was removed. This is that giant spatial scale. However, all of this that took decades to produce is just one snapshot of the subsurface. It does not give us any indication of how the ice sheet is changing in time. Now, we're working on that, because it turns out that the very first radar observations of Antarctica were collected using 35 millimeter optical film. And there were thousands of reels of this film in the archives of the museum of the Scott Polar Research Institute at the University of Cambridge.

So last summer, I took a state-of-the-art film scanner that was developed for digitizing Hollywood films and remastering them, and two art historians, and we went over to England, put on some gloves and archived and digitized all of that film. So that produced two million high-resolution images that my group is now working on analyzing and processing for comparing with contemporary conditions in the ice sheet. And, actually, that scanner—I found out about it from an archivist at the Academy of Motion Picture Arts and Sciences. So I'd like to thank the Academy—for making this possible.

And as amazing as it is that we can look at what was happening under the ice sheet 50 years ago, this is still just one more snapshot. It doesn't give us observations of the variation at the annual or seasonal scale that we know matters. There's some progress here, too. There are these recent ground-based radar systems that stay in one spot. So you take these radars and put them on the ice sheet and you bury a cache of car batteries. And you leave them out there for months or years at a time, and they send a pulse down into the ice sheet every so many minutes or hours. So this gives you continuous observation in time—but at one spot. So if you compare that imaging to the 2-D pictures provided by the airplane, this is just one vertical line. And this is pretty much where we are as a field right now. We can choose between good spatial coverage with airborne radar sounding and good temporal coverage in one spot with ground-based sounding.

But neither gives us what we really want: both at the same time. And if we're going to do that, we're going to need totally new ways of observing the ice sheet. And ideally, those should be extremely low-cost so that we can take lots of measurements from lots of sensors. Well, for existing radar systems, the biggest driver of cost is the power required to transmit the radar signal itself. So it'd be great if we were able to use existing radio systems or radio signals that are in the environment. And fortunately, the entire field of radio astronomy is built on the fact that there are bright radio signals in the sky. And a really bright one is our sun.

So, actually, one of the most exciting things my group is doing right now is trying to use the radio emissions from the sun as a type of radar signal. This is one of our field tests at Big Sur. That PVC pipe ziggurat is an antenna stand some undergrads in my lab built. And the idea here is that we stay out at Big Sur, and we watch the sunset in radio frequencies, and we try and detect the reflection of the sun off the surface of the ocean. Now, I know you're thinking, "There are no glaciers at Big Sur." And that's true.

But it turns out that detecting the reflection of the sun off the surface of the ocean and detecting the reflection off the bottom of an ice sheet are extremely geophysically similar. And if this works, we should be able to apply the same measurement principle in Antarctica. And this is not as far-fetched as it seems. The seismic industry has gone through a similar technique-development exercise, where they were able to move from detonating dynamite as a source, to using ambient seismic noise in the environment. And defense radars use TV signals and radio signals all the time, so they don't have to transmit a signal of radar and give away their position. So what I'm saying is this might really work. And if it does, we're going to need extremely low-cost sensors so we can deploy networks of hundreds or thousands of these on an ice sheet to do imaging.

And that's where the technological stars have really aligned to help us. Those earlier radar systems I talked about were developed by experienced engineers over the course of years at national facilities with expensive specialized equipment. But the recent developments in software-defined radio, rapid fabrication and the maker movement, make it so that it's possible for a team of teenagers working in my lab over the course of a handful of months to build a prototype radar. OK, they're not any teenagers, they're Stanford undergrads, but the point holds—that these enabling technologies are letting us break down the barrier between engineers who build instruments and scientists that use them. And by teaching engineering students to think like earth scientists and earth-science students who can think like engineers, my lab is building an environment in which we can build custom radar sensors for each problem at hand, that are optimized for low cost and high performance for that problem. And that's going to totally change the way we observe ice sheets.

Look, the sea level problem and the role of the cryosphere in sea level rise is extremely important and will affect the entire world. But that is not why I work on it. I work on it for the opportunity to teach and mentor extremely brilliant students, because I deeply believe that teams of hypertalented, hyperdriven, hyperpassionate young people can solve most of the challenges facing the world, and that providing the observations required to estimate sea level rise is just one of the many such problems they can and will solve.

Thank you.

播放本句

登入使用學習功能

使用Email登入

HOPE English 播放器使用小提示

  • 功能簡介

    單句重覆、重複上一句、重複下一句:以句子為單位重覆播放,單句重覆鍵顯示綠色時為重覆播放狀態;顯示白色時為正常播放狀態。按重複上一句、重複下一句時就會自動重覆播放該句。
    收錄佳句:點擊可增減想收藏的句子。

    中、英文字幕開關:中、英文字幕按鍵為綠色為開啟,灰色為關閉。鼓勵大家搞懂每一句的內容以後,關上字幕聽聽看,會發現自己好像在聽中文說故事一樣,會很有成就感喔!
    收錄單字:框選英文單字可以收藏不會的單字。
  • 分享
    如果您有收錄很優秀的句子時,可以分享佳句給大家,一同看佳句學英文!